Oracle® TimesTen In-Memory Database SQL Reference Release 11.2.1 Part Number E13070-09 |
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A search condition specifies criteria for choosing rows to select, update, or delete. Search conditions are parameters that can exist in clauses and expressions of any DML statements, such as INSERT...SELECT
, UPDATE
and CREATE VIEW
and some DDL statements, such as CREATE VIEW
.
A search condition is a single predicate or several predicates connected by the logical operators AND
or OR
. A predicate is an operation on expressions that evaluates to TRUE
, FALSE
, or UNKNOWN
. If a predicate evaluates to TRUE
for a row, the row qualifies for further processing. If the predicate evaluates to FALSE
or NULL
for a row, the row is not available for operations.
[NOT] {BetweenPredicate | ComparisonPredicate | InPredicate | LikePredicate| NullPredicate | InfinitePredicate | NaNPredicate | QuantifiedPredicate |(SearchCondition)} [{AND | OR} [NOT] {BetweenPredicate | ComparisonPredicate |InPredicate | LikePredicate|NullPredicate | QuantifiedPredicate |(SearchCondition)} ] [...]
Component | Description |
---|---|
NOT , AND , OR |
Logical operators with the following functions:
|
BetweenPredicate |
Determines whether an expression is within a certain range of values. For example: A BETWEEN B AND C is equivalent to A >= B AND A<= C . |
ComparisonPredicate |
Compares two expressions or list of two expressions using one of the operators < , <= , > , >= , = , <> . |
InPredicate |
Determines whether an expression or list of expressions matches an element within a specified set. |
ExistsPredicate |
Determines whether a subquery returns any row. |
LikePredicate |
Determines whether an expression contains a particular character string pattern. |
NullPredicate |
Determines whether a value is NULL . |
InfinitePredicate |
Determines whether an expression is infinite (positive or negative infinity). |
NaNPredicate |
Determines whether an expression is the undefined result of an operation ("not a number"). |
QuantifiedPredicate |
Determines whether an expression or list of expressions bears a particular relationship to a specified set. |
(SearchCondition ) |
One of the above predicates, enclosed in parentheses. |
Predicates in a search condition are evaluated as follows:
Predicates in parentheses are evaluated first.
NOT
is applied to each predicate.
AND
is applied next, left to right.
OR
is applied last, left to right.
Figure 4-1 shows the values that result from logical operations. A question mark (?
) represents the NULL
value.
Figure 4-1 Values that result from logical operations
When the search condition for a row evaluates to NULL
, the row does not satisfy the search condition and the row is not operated on.
You can compare only compatible data types.
TT_TINYINT
, TT_SMALLINT
, TT_INTEGER
, TT_BIGINT
, NUMBER
, BINARY_FLOAT
and BINARY_DOUBLE
are compatible.
CHAR
, VARCHAR2
, BINARY
, and VARBINARY
are compatible, regardless of length.
CHAR
, VARCHAR2
, NCHAR
, NVARCHAR2
, TT_TIME
, DATE
and TIMESTAMP
are compatible.
See Chapter 3, "Expressions" for information on value extensions during comparison operations.
See "Numeric data types" for information about how TimesTen compares values of different but compatible types.
The ALL
or NOT IN
predicate indicates that the operands on the left side of the comparison must compare in the same way with all of the values that the subquery returns. The ALL
predicate evaluates to TRUE
if the expression or list of expressions relates to all rows returned by the subquery as specified by the comparison operator. Similarly, the NOT IN
predicate evaluates to TRUE
if the expression or list of expressions does not equal the value returned by the subquery.
RowValueConstructor {CompOp ALL| NOT IN} (Subquery)
The syntax for RowValueConstructor
:
RowValueConstructorElement | (RowValueConstuctorList) | Subquery
The syntax for RowValueConstructorList
:
RowValueConstructorElement [{, RowValueConstructorElement} ... ]
The syntax for RowValueConstructorElement
:
Expression | NULL
The syntax for CompOp
:
{= | <> | > | >= | < | <= }
Component | Description |
---|---|
Expression |
The syntax of expressions is defined under "Expression specification". Both numeric and non-numeric expressions are allowed for ALL predicates, but both expression types must be compatible with each other. |
= |
Is equal to. |
<> |
Is not equal to. |
> |
Is greater than. |
>= |
Is greater than or equal to. |
< |
Is less than. |
<= |
Is less than or equal to. |
Subquery |
The syntax of subqueries is defined under "Subqueries" |
The ALL
predicate, which returns zero or more rows, uses a comparison operator modified with the keyword ALL
. See "Numeric data types" for information about how TimesTen compares values of different but compatible types.
If RowValueConstructorList
is specified only the operators =
and <>
are allowed.
Examples of NOT IN
with subqueries:
SELECT * FROM customers WHERE cid NOT IN (SELECT cust_id FROM returns) AND cid > 5000; SELECT * FROM customers WHERE cid NOT IN (SELECT cust_id FROM returns) AND cid NOT IN (SELECT cust_id FROM complaints); SELECT COUNT(*) From customers WHERE cid NOT IN (SELECT cust_id FROM returns) AND cid NOT IN (SELECT cust_id FROM complaints);
Select all books that are not from exclBookList
or if the price of the book is higher than $20.
SELECT * FROM books WHERE id NOT IN (SELECT id FROM exclBookList) OR books.price>20;
The following query returns the employee_id
and job_id
from the job_history table. It illustrates use of expression list and subquery with the NOT IN
predicate.
Command> SELECT employee_id, job_id FROM job_history > WHERE (employee_id, job_id) > NOT IN (SELECT employee_id, job_id FROM employees); < 101, AC_ACCOUNT > < 101, AC_MGR > < 102, IT_PROG > < 114, ST_CLERK > < 122, ST_CLERK > < 176, SA_MAN > < 200, AC_ACCOUNT > < 201, MK_REP > 8 rows found.
The ALL
/NOT IN
quantified predicate compares an expression or list of expressions with a list of specified values. The ALL
predicate evaluates to TRUE
if all the values in the ValueList
relate to the expression or list of expressions as indicated by the comparison operator. Similarly, the NOT IN
predicate evaluates to TRUE
if the expression or list of expressions does not equal one of the values in the list.
RowValueConstructor {CompOp ALL | NOT IN} ValueList
The syntax for RowValueConstructor
:
RowValueConstructorElement | (RowValueConstuctorList) |
The syntax for RowValueConstructorList
:
RowValueConstructorElement[{, RowValueConstructorElement} ... ]
The syntax for RowValueConstructorElement
:
Expression | NULL
The syntax for CompOp
:
{= | <> | > | >= | < | <= }
The syntax for more than one element in the ValueList
:
({Constant | ? | :DynamicParameter} [,...] )
The syntax for one element in the ValueList
not enclosed in parentheses:
Constant | ? | :DynamicParameter
The syntax for an empty ValueList
:
( )
The syntax for the ValueList
for a list of expressions:
(({Constant | ? | :DynamicParameter} [,...]))
Component | Description |
---|---|
Expression |
Specifies a value to be obtained. The values in ValueList must be compatible with the expression. For information on the syntax of expressions, see "Expression specification". |
= |
Is equal to. |
<> |
Is not equal to. |
> |
Is greater than. |
>= |
Is greater than or equal to. |
< |
Is less than. |
<= |
Is less than or equal to. |
ALL |
The predicate is TRUE if all the values in the ValueList relate to the expression or list of expressions as indicated by the comparison operator. |
ValueList |
A list of values that are compared against the expression's or list of expression's value. The ValueList cannot contain a column reference or a subquery. The ValueList can be nested if the left operand of the ValueList is a list.
Elements of the
|
If X
is the value of Expression
, and (a,b, ..., z)
represents the elements in ValueList
, and OP
is a comparison operator, then the following is true:
X OP ALL (a,b,...,z)
is equivalent to X OP a AND X OP b AND...AND X OP z
.
If X
is the value of Expression
and (a,b,..., z)
are the elements in a ValueList
, then the following is true:
X NOT IN (a,b,...,z)
is equivalent to NOT (X IN (a,b,...,z))
.
All character data types are compared in accordance with the current value of the NLS_SORT
session parameter.
NULL
cannot be specified in ValueList
.
See "Numeric data types" for information about how TimesTen compares values of different but compatible types.
NOT IN
or NOT EXISTS
with ALL
can be specified in an OR
expression.
IN
and EXISTS
with ALL
can be specified in an OR
expression.
When evaluating an empty ValueList
, the result of Expression
NOT IN
is true.
If RowValueConstructorList
is specified only the operators =
and <>
are allowed.
To query an empty select list for a NOT IN
condition:
SELECT * FROM t1 WHERE x1 NOT IN ();
An ANY
predicate compares two expressions using a comparison operator. The predicate evaluates to TRUE
if the first expression relates to anyrow returned by the subquery as specified by the comparison operator. Similarly, the IN
predicate compares an expression or list of expressions with a table subquery. The IN
predicate evaluates to TRUE
if the expression or list of expressions is equal to a value returned by a subquery.
RowValueConstructor {CompOp ANY| IN} (Subquery)
The syntax for RowValueConstructor
:
RowValueConstructorElement | (RowValueConstuctorList) | Subquery
The syntax for RowValueConstructorList
:
RowValueConstructorElement[{, RowValueConstructorElement} ... ]
The syntax for RowValueConstructorElement
:
Expression | NULL
The syntax for CompOp
:
{= | <> | > | >= | < | <= }
Component | Description |
---|---|
Expression |
The syntax of expressions is defined under "Expression specification". Both numeric and non-numeric expressions are allowed for ANY predicates, but both expression types must be compatible with each other. |
= |
Is equal to. |
<> |
Is not equal to. |
> |
Is greater than. |
>= |
Is greater than or equal to. |
< |
Is less than. |
<= |
Is less than or equal to. |
Subquery |
The syntax of subqueries is defined under "Subqueries". |
The ANY
predicate, which returns zero or more rows, uses a comparison operator modified with the keyword ANY
. See "Numeric data types" for information about how TimesTen compares values of different but compatible types.
This example retrieves a list of customers having at least one unshipped order:
SELECT customers.name FROM customers WHERE customers.id = ANY (SELECT orders.custid FROM orders WHERE orders.status = 'unshipped');
This is an example of an IN
predicate with subquery. It SELECT
s customers having at least one unshipped order:
SELECT customers.name FROM customers WHERE customers.id IN (SELECT orders.custid FROM orders WHERE orders.status = 'unshipped');
This example uses an aggregate query that specifies a subquery with IN
to find the maximum price of a book in the exclBookList
:
SELECT MAX(price) FROM books WHERE id IN (SELECT id FROM exclBookList);
This example illustrates the use of a list of expressions with the IN
predicate and a subquery.
SELECT * FROM t1 WHERE (x1,y1) IN (SELECT x2,y2 FROM t2);
This example illustrates the use of a list of expressions with the ANY
predicate and a subquery.
SELECT * FROM t1 WHERE (x1,y1) < ANY (SELECT x2,y2 FROM t2);
The following example illustrates the use of a list of expressions with the ANY
predicate.
Command> columnlabels on; Command> SELECT * FROM t1; X1, Y1 < 1, 2 > < 3, 4 > 2 rows found. Command> SELECT * FROM t2; X2, Y2 < 3, 4 > < 1, 2 > 2 rows found.
The ANY
/IN
quantified predicate compares an expression or list of expressions with a list of specified values. The ANY
predicate evaluates to TRUE
if one or more of the values in the ValueList relate to the expression or list of expressions as indicated by the comparison operator. Similarly, the IN
predicate evaluates to TRUE
if the expression or list of expressions is equal to one of the values in the list.
RowValueConstructor {CompOp {ANY| SOME} | IN} ValueList
The syntax for RowValueConstructor
:
RowValueConstructorElement | (RowValueConstuctorList) |
The syntax for RowValueConstructorList
:
RowValueConstructorElement[{, RowValueConstructorElement} ... ]
The syntax for RowValueConstructorElement
:
Expression | NULL
The syntax for CompOp
:
{= | <> | > | >= | < | <= }
The syntax for more than one element in the ValueList
:
({Constant | ? | :DynamicParameter} [,...] )
The syntax for one element in the ValueList
not enclosed in parentheses:
Constant | ? | :DynamicParameter
The syntax for an empty ValueList
:
( )
The syntax for the ValueList
for a list of expressions:
(({Constant | ? | :DynamicParameter} [,...]))
Component | Description |
---|---|
Expression |
Specifies a value to be obtained. The values in ValueList must be compatible with the expression. For information on the syntax of expressions, see "Expression specification". |
= |
Is equal to. |
<> |
Is not equal to. |
> |
Is greater than. |
>= |
Is greater than or equal to. |
< |
Is less than. |
<= |
Is less than or equal to. |
{ANY |
|
The predicate is TRUE if one or more of the values in the -ValueList relate to the expression or list of expressions as indicated by the comparison operator. SOME is a synonym for ANY . |
ValueList |
A list of values that are compared against the expression's or list of expression's value. The ValueList cannot contain a column reference or a subquery. The ValueList can be nested if the left operand of the ValueList is a list.
Elements of the
|
If X
is the value of Expression
, and (a,b, ..., z)
represents the elements in ValueList
, and OP
is a comparison operator, then the following is true:
X OP ANY (a,b,...,z)
is equivalent to X OP a OR X OP b OR...OR X OP z
.
If X
is the value of Expression
and (a,b,..., z)
are the elements in a ValueList
, then the following is true:
X IN (a,b,...,z)
is equivalent to X = a OR X = b OR...OR X = z
.
All character data types are compared in accordance with the current value of the NLS_SORT
session parameter.
NULL
cannot be specified in ValueList
.
See "Numeric data types" for information about how TimesTen compares values of different but compatible types.
When evaluating an empty ValueList
, the result of Expression
IN
is false.
Select all item numbers containing orders of 100, 200, or 300 items.
SELECT DISTINCT OrderItems.ItemNumber FROM OrderItems WHERE OrderItems.Quantity = ANY (100, 200, 300)
Get part numbers of parts whose weight is 12, 16, or 17.
SELECT Parts.PartNumber FROM Parts WHERE Parts.Weight IN (12, 16, 17);
Get part number of parts whose serial number is '1123-P-01'
, '1733-AD-01'
, :SerialNumber
or :SerialInd
, where :SerialNumber
and :SerialInd
are dynamic parameters whose values are supplied at runtime.
SELECT PartNumber FROM Purchasing.Parts WHERE SerialNumber IN ('1123-P-01', '1733-AD-01',:SerialNumber, :SerialInd);
To query an empty select list for IN
condition:
SELECT * FROM t1 WHERE x1 IN ();
Illustrates the use of a list of expressions with in:
SELECT * FROM t1 WHERE (x1,y1) IN ((1,2), (3,4));
The following example illustrates the use of a list of expressions for the IN
predicate. The query returns the department_name
for departments with department_id = 240
and location_id = 1700
.
Note:
The expression on the right side of theIN
predicate must be enclosed in double parentheses (( ))
.Command> SELECT department_name FROM departments > WHERE (department_id, location_id) IN ((240,1700)); < Government Sales > 1 row found.
A BETWEEN
predicate determines whether a value is:
Greater than or equal to a second value, and
Less than or equal to a third value.
The predicate evaluates to TRUE
if a value falls within the specified range.
Expression1 [NOT] BETWEEN Expression2 AND Expression3
Parameter | Description |
---|---|
Expression1 , Expression2 , Expression3 |
The syntax for expressions is defined in "Expression specification". Both numeric and non-numeric expressions are allowed in BETWEEN predicates, but all expressions must be compatible with each other. |
BETWEEN
evaluates to FALSE
and NOT BETWEEN
evaluates to TRUE
if the second value is greater than the third value.
Consult the following table if either Expression2
or Expression3
is NULL
for BETWEEN
or NOT BETWEEN
:
Expression2 | Expression3 | BETWEEN | NOT BETWEEN |
---|---|---|---|
<= Expression1 |
NULL |
NULL |
NULL |
> Expression1 |
NULL |
FALSE |
TRUE |
NULL |
>= Expression1 |
NULL |
NULL |
NULL |
< Expression1 |
NULL |
NULL |
Expression2
and Expression3
constitute a range of possible values for which Expression2
is the lowest possible value and Expression3
is the highest possible value within the specified range. In the BETWEEN
predicate, the low value must be specified first.
Comparisons are conducted as described in "Comparison predicate".
The BETWEEN
predicate is not supported for NCHAR
types.
Parts sold for under $250.00 and over $1500.00 are discounted 25 percent.
UPDATE Purchasing.Parts SET SalesPrice = SalesPrice * 0.75 WHERE SalesPrice NOT BETWEEN 250.00 AND 1500.00;
A comparison predicate compares two expressions using a comparison operator. The predicate evaluates to TRUE
if the first expression relates to the second expression as specified by the comparison operator.
RowValueConstructor CompOp RowValueConstructor2
The syntax for RowValueConstructor
:
RowValueConstructorElement | (RowValueConstuctorList) | ScalarSubquery
The syntax for RowValueConstructorList
:
RowValueConstructorElement[{, RowValueConstructorElement} ... ]
The syntax for RowValueConstructor2
(one expression)
Expression
The syntax for RowValueConstructor2
(list of expressions)
((Expression[,...]))
The syntax for CompOp
:
{= | <> | > | >= | < | <= }
Component | Description |
---|---|
Expression |
The syntax for expressions is defined under "Expression specification". Both numeric and non-numeric expressions are allowed in comparison predicates, but both expressions must be compatible with each other. |
ScalarSubquery |
A subquery that returns a single value. Scalar subqueries and their restrictions are defined under "Subqueries". |
= |
Is equal to. |
<> |
Is not equal to. |
> |
Is greater than. |
>= |
Is greater than or equal to. |
< |
Is less than. |
<= |
Is less than or equal to. |
All character data types are compared in accordance with the current value of the NLS_SORT
session parameter.
If RowValueConstructorList
is specified only the operators =
and <>
are allowed.
See "Numeric data types" for information about how TimesTen compares values of different but compatible types.
If either side of a comparison predicate evaluates to UNKNOWN
or NULL
, this implies that neither the predicate nor the negation of the predicate is TRUE
.
The NULL
value itself cannot be used directly as an operand of an operator or predicate. If used, it must be cast to the correct datatype. For example, (1 = NULL)
is not supported; however, (1 = CAST(NULL AS INT))
is supported. This is in compliance with the ANSI SQL-92 specification.
Retrieve part numbers of parts requiring fewer than 20 delivery days:
SELECT PartNumber FROM Purchasing.SupplyPrice WHERE DeliveryDays < 20;
The query returns the last_name
of employees where salary=9500
and commission_pct=.25
.
Note:
The expression on the right side of the equal sign must be enclosed in double parentheses(( ))
.Command> SELECT last_name FROM employees > WHERE(salary,commission_pct) = ((9500,.25)); < Bernstein > 1 row found.
The query returns the last_name
of the employee whose manager_id = 205
. The employee's department_id
and manager_id
is stored in both the employees
and departments
tables. A subquery is used to extract the information from the departments
table.
Command> SELECT last_name FROM employees > WHERE (department_id, manager_id) = > (SELECT department_id, manager_id FROM departments > WHERE manager_id = 205); < Gietz > 1 row found.
An EXISTS
predicate checks for the existence or nonexistence of a table subquery. The predicate evaluates to TRUE
if the subquery returns at least one row for EXISTS
and no rows for NOT EXISTS
[NOT] EXISTS (Subquery)
The EXISTS
predicate has the following parameter:
Parameter | Description |
---|---|
Subquery |
The syntax of subqueries is defined under "Subqueries" |
When a subquery is introduced with EXISTS
, the subquery functions as an existence test. EXISTS
tests for the presence or absence of an empty set of rows. If the subquery returns at least one row, the subquery evaluates to true.
When a subquery is introduced with NOT EXISTS
, the subquery functions as an absence test. NOT EXISTS
tests for the presence or absence of an empty set of rows. If the subquery returns no rows, the subquery evaluates to true.
If join order is issued using the ttOptSetOrder
built-in procedure that conflicts with the join ordering requirements of the NOT EXISTS
subquery, the specified join order is ignored, TimesTen issues a warning and the query is executed.
The following table describes supported and unsupported usages of EXISTS
and NOT EXISTS
in TimesTen;
Query/subquery description | Not Exists | Exists |
---|---|---|
Aggregates in subquery | Supported | Supported |
Aggregates in main query | Supported | Supported |
Subquery in OR clause |
Supported | Supported |
Join ordering using the ttOptSetOrder built-in procedure |
Limited support | Supported |
Get a list of customers having at least one unshipped order.
SELECT customers.name FROM customers WHERE EXISTS (SELECT 1 FROM orders WHERE customers.id = orders.custid AND orders.status = 'unshipped');
Get a list of customers having no unshipped orders.
SELECT customers.name FROM customers WHERE NOT EXISTS (SELECT 1 FROM orders WHERE customers.id = orders.custid AND orders.status = 'unshipped');
An IS INFINITE
predicate determines whether an expression is infinite (positive infinity (INF
) or negative infinity (-INF
)).
Expression IS [NOT] INFINITE
An IS INFINITE
predicate evaluates to TRUE
if the expression is positive or negative infinity.
An IS NOT INFINITE
predicate evaluates to TRUE
if expression is neither positive nor negative infinity.
The expression must either resolve to a numeric data type or to a data type that can be implicitly converted to a numeric data type.
Two positive infinity values are equal to each other. Two negative infinity values are equal to each other.
Expressions containing floating-point values may generate Inf
, -Inf
, or NaN
. This can occur either because the expression generated overflow or exceptional conditions or because one or more of the values in the expression was Inf
, -Inf
, or NaN
. Inf and NaN
are generated in overflow or division by 0 conditions.
Inf
, -Inf
, and NaN
values are not ignored in aggregate functions. NULL
values are. If you want to exclude Inf
and NaN
from aggregates (or from any selection), use both the IS NOT NAN
and IS NOT INFINITE
predicates.
Negative infinity (-INF
) sorts lower than all other values. Positive infinity (INF
) sorts higher than all other values, but lower than NaN
("not a number") and the NULL
value.
For more information on Inf
and NaN
, see "INF and NAN".
An IS NAN
predicate determines whether an expression is the undefined result of an operation (that is, is "not a number" or NaN
).
Expression IS [NOT] NAN
An IS NAN
predicate evaluates to TRUE
if the expression is "not a number."
An IS NOT NAN
predicate evaluates to TRUE
if expression is not "not a number."
The expression must either resolve to a numeric data type or to a data type that can be implicitly converted to a numeric data type.
Two NaN
("not a number") values are equal to each other.
Expressions containing floating-point values may generate Inf
, -Inf
, or NaN
. This can occur either because the expression generated overflow or exceptional conditions or because one or more of the values in the expression was Inf
, -Inf
, or NaN
. Inf
and NaN
are generated in overflow or division by 0 conditions.
Inf
, -Inf
, and NaN
values are not ignored in aggregate functions. NULL
values are. If you want to exclude Inf
and NaN
from aggregates (or from any selection), use both the IS NOT NAN
and IS NOT INFINITE
predicates.
NaN
("not a number") sorts higher than all other values including positive infinity, but lower than the NULL
value.
For more information on Inf
and NaN
, see "INF and NAN".
An IS NULL
predicate determines whether an expression has the value NULL
. The predicate evaluates to TRUE
if the expression is NULL
. If the NOT
option is used, the predicate evaluates to TRUE
if the expression is NOT NULL
.
{ColumnName | Constant | (Expression)} IS [NOT] NULL
Parameter | Description |
---|---|
ColumnName |
The name of a column from which a value is to be taken. Column names are discussed in Chapter 2, "Names, Namespace and Parameters". |
Constant |
A specific value. See "Constants". |
(Expression ) |
Expression to test. |
Vendors with no personal contact names are identified.
SELECT * FROM Purchasing.Vendors WHERE ContactName IS NULL;
A LIKE
predicate determines whether a CHAR
, VARCHAR2
, NCHAR
, or NVARCHAR2
expression contains a given pattern. The predicate evaluates to TRUE
if an expression contains the pattern.
Expression [NOT] LIKE {'PatternString'| {? | :DynamicParameter}} [ESCAPE {'EscapeChar' | {? | :DynamicParameter}}]
Parameter | Description |
---|---|
Expression |
The syntax of expressions is presented in Chapter 3, "Expressions". |
PatternString |
Describes what you are searching for in the expression. The pattern may consist of characters only (including digits and special characters). For example, NAME LIKE 'Annie' evaluates to TRUE only for a name of Annie with no spaces. Upper case and lower case are significant.
You can also use the predicate to test for a partial match by using the following symbols in the pattern:
For example:
For example, You can use the |
EscapeChar |
Describes an optional escape character which can be used to interpret the symbols _ and % literally in the pattern.
The escape character must be a single character. When it appears in the pattern, it must be followed by the escape character itself, the |
? | Indicates a dynamic parameter in a prepared SQL statement. The parameter value is supplied when the statement is executed. |
As long as no escape character is specified, the _
or %
in the pattern acts as a wild card character. If an escape character is specified, then the wild card or escape character that follows is treated literally. If the character following an escape character is not a wild card or the escape character, an error results.
If the value of the expression, the pattern, or the escape character is NULL
, then the LIKE
predicate evaluates to NULL
and the row is not operated on.
Find employees whose last name begins with 'Sm'
.
Command> SELECT employee_id, last_name,first_name FROM employees > WHERE last_name LIKE 'Sm%' > ORDER BY employee_id,last_name,first_name; < 159, Smith, Lindsey > < 171, Smith, William > 2 rows found.
Find employees whose last name begins with 'SM'
. This query returns no results because there are no employees whose last_name
begins with 'SM'
.
Command> SELECT employee_id, last_name,first_name from employees > WHERE last_name LIKE 'SM%' > ORDER BY employee_id,last_name,first_name; 0 rows found.
Use a dynamic parameter denoted by ?
to find employees whose last name begins with 'Sm'
at execution time.
Command> SELECT employee_id, last_name,first_name FROM employees > WHERE last_name like ? > ORDER BY employee_id,last_name,first_name; Type '?' for help on entering parameter values. Type '*' to end prompting and abort the command. Type '-' to leave the parameter unbound. Type '/;' to leave the remaining parameters unbound and execute the command. Enter Parameter 1 '_QMARK_1' (VARCHAR2) > 'Sm%' < 159, Smith, Lindsey > < 171, Smith, William > 2 rows found.
Use a bind variable denoted by :a
to find employees whose last name begins with 'Sm'
at execution time.
Command> SELECT employee_id, last_name,first_name FROM employees > WHERE last_name LIKE :a > ORDER BY employee_id,last_name,first_name; Type '?' for help on entering parameter values. Type '*' to end prompting and abort the command. Type '-' to leave the parameter unbound. Type '/;' to leave the remaining parameters unbound and execute the command. Enter Parameter 1 'A' (VARCHAR2) > 'Sm%' < 159, Smith, Lindsey > < 171, Smith, William > 2 rows found.
For employees whose last name begins with 'Smit'
, find the last name of the manager. Display the first name and last name of the employee and the last name of the manager.
Command> SELECT e1.first_name || ' ' || e1.last_name||' works for '||e2.last_name > FROM employees e1, employees e2 > WHERE e1.manager_id = e2.employee_id > AND e1.last_name like 'Smit'; < Lindsey Smith works for Partners > < William Smith works for Cambrault > 2 rows found.
This query results in an error because the pattern references a column.
Command> SELECT e1.first_name || ' ' || e1.last_name||' works for '||e2.last_name > FROM employees e1, employees e2 > WHERE e1.manager_id = e2.employee_id > AND 'Smith' like e1.last_name; 1001: Syntax error in SQL statement before or at: "E1", character position: 169 ...nager_id = e2.employee_id AND 'Smith' like e1.last_name ^^ The command failed.
The LIKE
predicate can be used for pattern matching of NCHAR
and NVARCHAR2
strings. The pattern matching characters are:
Character | Description |
---|---|
U+005F SPACING UNDERSCORE |
Represents any single Unicode character. |
U+0025 PERCENT SIGN |
Represents any string of zero or more Unicode characters. |
The escape character is similarly supported as a single Unicode character or parameter.
The types of the LIKE
operands can be any combination of character types.
Case-insensitive and accent-insensitive NLS_SORT
is supported with the LIKE
predicate.
In these examples, the Unicode character U+0021 EXCLAMATION MARK
is being used to escape the Unicode character U+005F SPACING UNDERSCORE
. Unicode character U+0025 PERCENT SIGN
is not escaped, and assumes its pattern matching meaning.
VendorName
is an NCHAR
or NVARCHAR2
column.
SELECT VendorName FROM Purchasing.Vendors WHERE VendorName LIKE N'ACME!_%' ESCAPE N'!';
This example is equivalent:
SELECT VendorName FROM Purchasing.Vendors WHERE VendorName LIKE N'ACME!\u005F\u0025' ESCAPE N'!';