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PostgreSQL documentation

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</sect2>

<sect2>

<title><literal>IN</literal> (scalar form)</title>

<synopsis>

<replaceable>expression</replaceable> IN (<replaceable>value</replaceable><optional>, ...</optional>)

</synopsis>

<para>

The right-hand side of this form of <token>IN</token> is a parenthesized list

of scalar expressions. The result is <quote>true</> if the left-hand expression's

result is equal to any of the right-hand expressions. This is a shorthand

notation for

<synopsis>

<replaceable>expression</replaceable> = <replaceable>value1</replaceable>

OR

<replaceable>expression</replaceable> = <replaceable>value2</replaceable>

OR

...

</synopsis>

</para>

<para>

Note that if the left-hand expression yields null, or if there are

no equal right-hand values and at least one right-hand expression yields

null, the result of the <token>IN</token> construct will be null, not false.

This is in accordance with SQL's normal rules for Boolean combinations

of null values.

</para>

<note>

<para>

This form of <token>IN</token> is not truly a subquery expression, but it

seems best to document it in the same place as subquery <token>IN</token>.

</para>

</note>

</sect2>

<sect2>

<title><literal>IN</literal> (subquery form)</title>

<title><literal>IN</literal></title>

<synopsis>

<replaceable>expression</replaceable> IN (<replaceable>subquery</replaceable>)

</synopsis>

<para>

The right-hand sideof this form of <token>IN</token>is a parenthesized

The right-hand side is a parenthesized

subquery, which must return exactly one column. The left-hand expression

is evaluated and compared to each row of the subquery result.

The result of <token>IN</token> is <quote>true</> if any equal subquery row is found.

</para>

<para>

As usual, null values in theexpressions or subqueryrows are combined per

As usual, null values in the rows are combined per

the normal rules of SQL Boolean expressions. Two rows are considered

equal if all their corresponding members are non-null and equal; the rows

are unequal if any corresponding members are non-null and unequal;

</sect2>

<sect2>

<title><literal>NOT IN</literal> (scalar form)</title>

<synopsis>

<replaceable>expression</replaceable> NOT IN (<replaceable>value</replaceable><optional>, ...</optional>)

</synopsis>

<para>

The right-hand side of this form of <token>NOT IN</token> is a parenthesized list

of scalar expressions. The result is <quote>true</quote> if the left-hand expression's

result is unequal to all of the right-hand expressions. This is a shorthand

notation for

<synopsis>

<replaceable>expression</replaceable> &lt;&gt; <replaceable>value1</replaceable>

AND

<replaceable>expression</replaceable> &lt;&gt; <replaceable>value2</replaceable>

AND

...

</synopsis>

</para>

<para>

Note that if the left-hand expression yields null, or if there are

no equal right-hand values and at least one right-hand expression yields

null, the result of the <token>NOT IN</token> construct will be null, not true

as one might naively expect.

This is in accordance with SQL's normal rules for Boolean combinations

of null values.

</para>

<tip>

<para>

<literal>x NOT IN y</literal> is equivalent to <literal>NOT (x IN y)</literal> in all

cases. However, null values are much more likely to trip up the novice when

working with <token>NOT IN</token> than when working with <token>IN</token>.

It's best to express your condition positively if possible.

</para>

</tip>

</sect2>

<sect2>

<title><literal>NOT IN </literal>(subquery form)</title>

<title><literal>NOT IN </literal></title>

<synopsis>

<replaceable>expression</replaceable> NOT IN (<replaceable>subquery</replaceable>)

</synopsis>

<para>

The right-hand sideof this form of <token>NOT IN</token>is a parenthesized

The right-hand side is a parenthesized

subquery, which must return exactly one column. The left-hand expression

is evaluated and compared to each row of the subquery result.

The result of <token>NOT IN</token> is <quote>true</> if only unequal subquery rows

</para>

<para>

As usual, null values in theexpressions or subqueryrows are combined per

As usual, null values in the rows are combined per

the normal rules of SQL Boolean expressions. Two rows are considered

equal if all their corresponding members are non-null and equal; the rows

are unequal if any corresponding members are non-null and unequal;

</synopsis>

<para>

The right-hand sideof this form of <token>ANY</token>is a parenthesized

The right-hand side is a parenthesized

subquery, which must return exactly one column. The left-hand expression

is evaluated and compared to each row of the subquery result using the

given <replaceable>operator</replaceable>, which must yield a Boolean

</para>

<para>

As usual, null values in theexpressions or subqueryrows are combined per

As usual, null values in the rows are combined per

the normal rules of SQL Boolean expressions. Two rows are considered

equal if all their corresponding members are non-null and equal; the rows

are unequal if any corresponding members are non-null and unequal;

</synopsis>

<para>

The right-hand sideof this form of <token>ALL</token>is a parenthesized

The right-hand side is a parenthesized

subquery, which must return exactly one column. The left-hand expression

is evaluated and compared to each row of the subquery result using the

given <replaceable>operator</replaceable>, which must yield a Boolean

</para>

<para>

As usual, null values in theexpressions or subqueryrows are combined per

As usual, null values in the rows are combined per

the normal rules of SQL Boolean expressions. Two rows are considered

equal if all their corresponding members are non-null and equal; the rows

are unequal if any corresponding members are non-null and unequal;

<synopsis>

(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</replaceable> (<replaceable>subquery</replaceable>)

(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</replaceable> (<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>)

</synopsis>

<para>

The left-hand side is a list of scalar expressions. The right-hand side

can be either a list of scalar expressions of the same length, or a

parenthesized subquery, which must return exactly as many columns as there

The left-hand side is a list of scalar expressions. The right-hand side is

a parenthesized subquery, which must return exactly as many columns as there

are expressions on the left-hand side. Furthermore, the subquery cannot

return more than one row. (If it returns zero rows, the result is taken to

be null.) The left-hand side is evaluated and compared row-wise to the

single subquery result row, or to the right-hand expression list.

single subquery result row.

Presently, only <literal>=</literal> and <literal>&lt;&gt;</literal> operators are allowed

in row-wise comparisons.

The result is <quote>true</> if the two rows are equal or unequal, respectively.

</para>

<para>

As usual, null values in the rows are combined per

the normal rules of SQL Boolean expressions. Two rows are considered

equal if all their corresponding members are non-null and equal; the rows

are unequal if any corresponding members are non-null and unequal;

otherwise the result of the row comparison is unknown (null).

</para>

</sect2>

</sect1>

<sect1 id="functions-comparisons">

<title>Row and Array Comparisons</title>

<indexterm>

<primary>in</primary>

</indexterm>

<indexterm>

<primary>not in</primary>

</indexterm>

<indexterm>

<primary>any</primary>

</indexterm>

<indexterm>

<primary>all</primary>

</indexterm>

<indexterm>

<primary>some</primary>

</indexterm>

<para>

This section describes several specialized constructs for making

multiple comparisons between groups of values. These forms are

syntactically related to the subquery forms of the previous section,

but do not involve subqueries.

The forms involving array subexpressions are

<productname>PostgreSQL</productname> extensions; the rest are

<acronym>SQL</acronym>-compliant.

All of the expression forms documented in this section return

Boolean (true/false) results.

</para>

<sect2>

<title><literal>IN</literal></title>

<synopsis>

<replaceable>expression</replaceable> IN (<replaceable>value</replaceable><optional>, ...</optional>)

</synopsis>

<para>

The right-hand side is a parenthesized list

of scalar expressions. The result is <quote>true</> if the left-hand expression's

result is equal to any of the right-hand expressions. This is a shorthand

notation for

<synopsis>

<replaceable>expression</replaceable> = <replaceable>value1</replaceable>

OR

<replaceable>expression</replaceable> = <replaceable>value2</replaceable>

OR

...

</synopsis>

</para>

<para>

Note that if the left-hand expression yields null, or if there are

no equal right-hand values and at least one right-hand expression yields

null, the result of the <token>IN</token> construct will be null, not false.

This is in accordance with SQL's normal rules for Boolean combinations

of null values.

</para>

</sect2>

<sect2>

<title><literal>NOT IN</literal></title>

<synopsis>

<replaceable>expression</replaceable> NOT IN (<replaceable>value</replaceable><optional>, ...</optional>)

</synopsis>

<para>

The right-hand side is a parenthesized list

of scalar expressions. The result is <quote>true</quote> if the left-hand expression's

result is unequal to all of the right-hand expressions. This is a shorthand

notation for

<synopsis>

<replaceable>expression</replaceable> &lt;&gt; <replaceable>value1</replaceable>

AND

<replaceable>expression</replaceable> &lt;&gt; <replaceable>value2</replaceable>

AND

...

</synopsis>

</para>

<para>

Note that if the left-hand expression yields null, or if there are

no equal right-hand values and at least one right-hand expression yields

null, the result of the <token>NOT IN</token> construct will be null, not true

as one might naively expect.

This is in accordance with SQL's normal rules for Boolean combinations

of null values.

</para>

<tip>

<para>

<literal>x NOT IN y</literal> is equivalent to <literal>NOT (x IN y)</literal> in all

cases. However, null values are much more likely to trip up the novice when

working with <token>NOT IN</token> than when working with <token>IN</token>.

It's best to express your condition positively if possible.

</para>

</tip>

</sect2>

<sect2>

<title><literal>ANY</literal>/<literal>SOME</literal> (array)</title>

<synopsis>

<replaceable>expression</replaceable> <replaceable>operator</replaceable> ANY (<replaceable>array expression</replaceable>)

<replaceable>expression</replaceable> <replaceable>operator</replaceable> SOME (<replaceable>array expression</replaceable>)

</synopsis>

<para>

The right-hand side is a parenthesized expression, which must yield an

array value.

The left-hand expression

is evaluated and compared to each element of the array using the

given <replaceable>operator</replaceable>, which must yield a Boolean

result.

The result of <token>ANY</token> is <quote>true</> if any true result is obtained.

The result is <quote>false</> if no true result is found (including the special

case where the array has zero elements).

</para>

<para>

<token>SOME</token> is a synonym for <token>ANY</token>.

</para>

</sect2>

<sect2>

<title><literal>ALL</literal> (array)</title>

<synopsis>

<replaceable>expression</replaceable> <replaceable>operator</replaceable> ALL (<replaceable>array expression</replaceable>)

</synopsis>

<para>

The right-hand side is a parenthesized expression, which must yield an

array value.

The left-hand expression

is evaluated and compared to each element of the array using the

given <replaceable>operator</replaceable>, which must yield a Boolean

result.

The result of <token>ALL</token> is <quote>true</> if all comparisons yield true

(including the special case where the array has zero elements).

The result is <quote>false</> if any false result is found.

</para>

</sect2>

<sect2>

<title>Row-wise Comparison</title>

<synopsis>

(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</replaceable> (<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>)

</synopsis>

<para>

Each side is a list of scalar expressions; the two lists must be

of the same length. Each side is evaluated and they are compared

row-wise.

Presently, only <literal>=</literal> and <literal>&lt;&gt;</literal> operators are allowed

in row-wise comparisons.

The result is <quote>true</> if the two rows are equal or unequal, respectively.

</para>

<para>

As usual, null values in theexpressions or subqueryrows are combined per

As usual, null values in the rows are combined per

the normal rules of SQL Boolean expressions. Two rows are considered

equal if all their corresponding members are non-null and equal; the rows

are unequal if any corresponding members are non-null and unequal;