Sophie: postgresql9.6-docs-9.6.22-1.mga7 noarch

postgresql9.6-docs-9.6.22-1.mga7.noarch.rpm

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Subquery Expressions</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REV="MADE"
HREF="mailto:pgsql-docs@postgresql.org"><LINK
REL="HOME"
TITLE="PostgreSQL 9.6.22 Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="Functions and Operators"
HREF="functions.html"><LINK
REL="PREVIOUS"
TITLE="Window Functions"
HREF="functions-window.html"><LINK
REL="NEXT"
TITLE="Row and Array Comparisons"
HREF="functions-comparisons.html"><LINK
REL="STYLESHEET"
TYPE="text/css"
HREF="stylesheet.css"><META
HTTP-EQUIV="Content-Type"
CONTENT="text/html; charset=ISO-8859-1"><META
NAME="creation"
CONTENT="2021-05-18T09:16:10"></HEAD
><BODY
CLASS="SECT1"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="4"
ALIGN="center"
VALIGN="bottom"
><A
HREF="index.html"
>PostgreSQL 9.6.22 Documentation</A
></TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
TITLE="Window Functions"
HREF="functions-window.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="functions.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="60%"
ALIGN="center"
VALIGN="bottom"
>Chapter 9. Functions and Operators</TD
><TD
WIDTH="20%"
ALIGN="right"
VALIGN="top"
><A
TITLE="Row and Array Comparisons"
HREF="functions-comparisons.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="FUNCTIONS-SUBQUERY"
>9.22. Subquery Expressions</A
></H1
><P
>   This section describes the <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
>-compliant subquery
   expressions available in <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>.
   All of the expression forms documented in this section return
   Boolean (true/false) results.
  </P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="FUNCTIONS-SUBQUERY-EXISTS"
>9.22.1. <TT
CLASS="LITERAL"
>EXISTS</TT
></A
></H2
><PRE
CLASS="SYNOPSIS"
>EXISTS (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   The argument of <TT
CLASS="TOKEN"
>EXISTS</TT
> is an arbitrary <TT
CLASS="COMMAND"
>SELECT</TT
> statement,
   or <I
CLASS="FIRSTTERM"
>subquery</I
>.  The
   subquery is evaluated to determine whether it returns any rows.
   If it returns at least one row, the result of <TT
CLASS="TOKEN"
>EXISTS</TT
> is
   <SPAN
CLASS="QUOTE"
>"true"</SPAN
>; if the subquery returns no rows, the result of <TT
CLASS="TOKEN"
>EXISTS</TT
>
   is <SPAN
CLASS="QUOTE"
>"false"</SPAN
>.
  </P
><P
>   The subquery can refer to variables from the surrounding query,
   which will act as constants during any one evaluation of the subquery.
  </P
><P
>   The subquery will generally only be executed long enough to determine
   whether at least one row is returned, not all the way to completion.
   It is unwise to write a subquery that has side effects (such as
   calling sequence functions); whether the side effects occur
   might be unpredictable.
  </P
><P
>   Since the result depends only on whether any rows are returned,
   and not on the contents of those rows, the output list of the
   subquery is normally unimportant.  A common coding convention is
   to write all <TT
CLASS="LITERAL"
>EXISTS</TT
> tests in the form
   <TT
CLASS="LITERAL"
>EXISTS(SELECT 1 WHERE ...)</TT
>.  There are exceptions to
   this rule however, such as subqueries that use <TT
CLASS="TOKEN"
>INTERSECT</TT
>.
  </P
><P
>   This simple example is like an inner join on <TT
CLASS="LITERAL"
>col2</TT
>, but
   it produces at most one output row for each <TT
CLASS="LITERAL"
>tab1</TT
> row,
   even if there are several matching <TT
CLASS="LITERAL"
>tab2</TT
> rows:
</P><PRE
CLASS="SCREEN"
>SELECT col1
FROM tab1
WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2);</PRE
><P>
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="FUNCTIONS-SUBQUERY-IN"
>9.22.2. <TT
CLASS="LITERAL"
>IN</TT
></A
></H2
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>expression</I
></TT
> IN (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   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 <TT
CLASS="TOKEN"
>IN</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if any equal subquery row is found.
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if no equal row is found (including the
   case where the subquery returns no rows).
  </P
><P
>   Note that if the left-hand expression yields null, or if there are
   no equal right-hand values and at least one right-hand row yields
   null, the result of the <TT
CLASS="TOKEN"
>IN</TT
> construct will be null, not false.
   This is in accordance with SQL's normal rules for Boolean combinations
   of null values.
  </P
><P
>   As with <TT
CLASS="TOKEN"
>EXISTS</TT
>, it's unwise to assume that the subquery will
   be evaluated completely.
  </P
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>row_constructor</I
></TT
> IN (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   The left-hand side of this form of <TT
CLASS="TOKEN"
>IN</TT
> is a row constructor,
   as described in <A
HREF="sql-expressions.html#SQL-SYNTAX-ROW-CONSTRUCTORS"
>Section 4.2.13</A
>.
   The right-hand side is a parenthesized
   subquery, which must return exactly as many columns as there are
   expressions in the left-hand row.  The left-hand expressions are
   evaluated and compared row-wise to each row of the subquery result.
   The result of <TT
CLASS="TOKEN"
>IN</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if any equal subquery row is found.
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if no equal row is found (including the
   case where the subquery returns no rows).
  </P
><P
>   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 that row comparison is unknown (null).
   If all the per-row results are either unequal or null, with at least one
   null, then the result of <TT
CLASS="TOKEN"
>IN</TT
> is null.
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="FUNCTIONS-SUBQUERY-NOTIN"
>9.22.3. <TT
CLASS="LITERAL"
>NOT IN</TT
></A
></H2
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>expression</I
></TT
> NOT IN (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   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 <TT
CLASS="TOKEN"
>NOT IN</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if only unequal subquery rows
   are found (including the case where the subquery returns no rows).
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if any equal row is found.
  </P
><P
>   Note that if the left-hand expression yields null, or if there are
   no equal right-hand values and at least one right-hand row yields
   null, the result of the <TT
CLASS="TOKEN"
>NOT IN</TT
> construct will be null, not true.
   This is in accordance with SQL's normal rules for Boolean combinations
   of null values.
  </P
><P
>   As with <TT
CLASS="TOKEN"
>EXISTS</TT
>, it's unwise to assume that the subquery will
   be evaluated completely.
  </P
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>row_constructor</I
></TT
> NOT IN (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   The left-hand side of this form of <TT
CLASS="TOKEN"
>NOT IN</TT
> is a row constructor,
   as described in <A
HREF="sql-expressions.html#SQL-SYNTAX-ROW-CONSTRUCTORS"
>Section 4.2.13</A
>.
   The right-hand side is a parenthesized
   subquery, which must return exactly as many columns as there are
   expressions in the left-hand row.  The left-hand expressions are
   evaluated and compared row-wise to each row of the subquery result.
   The result of <TT
CLASS="TOKEN"
>NOT IN</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if only unequal subquery rows
   are found (including the case where the subquery returns no rows).
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if any equal row is found.
  </P
><P
>   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 that row comparison is unknown (null).
   If all the per-row results are either unequal or null, with at least one
   null, then the result of <TT
CLASS="TOKEN"
>NOT IN</TT
> is null.
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="FUNCTIONS-SUBQUERY-ANY-SOME"
>9.22.4. <TT
CLASS="LITERAL"
>ANY</TT
>/<TT
CLASS="LITERAL"
>SOME</TT
></A
></H2
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>expression</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> ANY (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)
<TT
CLASS="REPLACEABLE"
><I
>expression</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> SOME (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   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 <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
>, which must yield a Boolean
   result.
   The result of <TT
CLASS="TOKEN"
>ANY</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if any true result is obtained.
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if no true result is found (including the
   case where the subquery returns no rows).
  </P
><P
>   <TT
CLASS="TOKEN"
>SOME</TT
> is a synonym for <TT
CLASS="TOKEN"
>ANY</TT
>.
   <TT
CLASS="TOKEN"
>IN</TT
> is equivalent to <TT
CLASS="LITERAL"
>= ANY</TT
>.
  </P
><P
>   Note that if there are no successes and at least one right-hand row yields
   null for the operator's result, the result of the <TT
CLASS="TOKEN"
>ANY</TT
> construct
   will be null, not false.
   This is in accordance with SQL's normal rules for Boolean combinations
   of null values.
  </P
><P
>   As with <TT
CLASS="TOKEN"
>EXISTS</TT
>, it's unwise to assume that the subquery will
   be evaluated completely.
  </P
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>row_constructor</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> ANY (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)
<TT
CLASS="REPLACEABLE"
><I
>row_constructor</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> SOME (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   The left-hand side of this form of <TT
CLASS="TOKEN"
>ANY</TT
> is a row constructor,
   as described in <A
HREF="sql-expressions.html#SQL-SYNTAX-ROW-CONSTRUCTORS"
>Section 4.2.13</A
>.
   The right-hand side is a parenthesized
   subquery, which must return exactly as many columns as there are
   expressions in the left-hand row.  The left-hand expressions are
   evaluated and compared row-wise to each row of the subquery result,
   using the given <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
>.
   The result of <TT
CLASS="TOKEN"
>ANY</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if the comparison
   returns true for any subquery row.
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if the comparison returns false for every
   subquery row (including the case where the subquery returns no
   rows).
   The result is NULL if no comparison with a subquery row returns true,
   and at least one comparison returns NULL.
  </P
><P
>   See <A
HREF="functions-comparisons.html#ROW-WISE-COMPARISON"
>Section 9.23.5</A
> for details about the meaning
   of a row constructor comparison.
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="FUNCTIONS-SUBQUERY-ALL"
>9.22.5. <TT
CLASS="LITERAL"
>ALL</TT
></A
></H2
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>expression</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> ALL (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   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 <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
>, which must yield a Boolean
   result.
   The result of <TT
CLASS="TOKEN"
>ALL</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if all rows yield true
   (including the case where the subquery returns no rows).
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if any false result is found.
   The result is NULL if no comparison with a subquery row returns false,
   and at least one comparison returns NULL.
  </P
><P
>   <TT
CLASS="TOKEN"
>NOT IN</TT
> is equivalent to <TT
CLASS="LITERAL"
>&lt;&gt; ALL</TT
>.
  </P
><P
>   As with <TT
CLASS="TOKEN"
>EXISTS</TT
>, it's unwise to assume that the subquery will
   be evaluated completely.
  </P
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>row_constructor</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> ALL (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   The left-hand side of this form of <TT
CLASS="TOKEN"
>ALL</TT
> is a row constructor,
   as described in <A
HREF="sql-expressions.html#SQL-SYNTAX-ROW-CONSTRUCTORS"
>Section 4.2.13</A
>.
   The right-hand side is a parenthesized
   subquery, which must return exactly as many columns as there are
   expressions in the left-hand row.  The left-hand expressions are
   evaluated and compared row-wise to each row of the subquery result,
   using the given <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
>.
   The result of <TT
CLASS="TOKEN"
>ALL</TT
> is <SPAN
CLASS="QUOTE"
>"true"</SPAN
> if the comparison
   returns true for all subquery rows (including the
   case where the subquery returns no rows).
   The result is <SPAN
CLASS="QUOTE"
>"false"</SPAN
> if the comparison returns false for any
   subquery row.
   The result is NULL if no comparison with a subquery row returns false,
   and at least one comparison returns NULL.
  </P
><P
>   See <A
HREF="functions-comparisons.html#ROW-WISE-COMPARISON"
>Section 9.23.5</A
> for details about the meaning
   of a row constructor comparison.
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN21208"
>9.22.6. Single-row Comparison</A
></H2
><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>row_constructor</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
> (<TT
CLASS="REPLACEABLE"
><I
>subquery</I
></TT
>)</PRE
><P
>   The left-hand side is a row constructor,
   as described in <A
HREF="sql-expressions.html#SQL-SYNTAX-ROW-CONSTRUCTORS"
>Section 4.2.13</A
>.
   The right-hand side is a parenthesized subquery, which must return exactly
   as many columns as there are expressions in the left-hand row. 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.
  </P
><P
>   See <A
HREF="functions-comparisons.html#ROW-WISE-COMPARISON"
>Section 9.23.5</A
> for details about the meaning
   of a row constructor comparison.
  </P
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="functions-window.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="functions-comparisons.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Window Functions</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="functions.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Row and Array Comparisons</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>