diff options
| -rw-r--r-- | doc/src/sgml/ref/create_table_as.sgml | 52 | ||||
| -rw-r--r-- | doc/src/sgml/ref/select.sgml | 38 | ||||
| -rw-r--r-- | doc/src/sgml/ref/select_into.sgml | 85 |
3 files changed, 113 insertions, 62 deletions
diff --git a/doc/src/sgml/ref/create_table_as.sgml b/doc/src/sgml/ref/create_table_as.sgml index a93989586ac..47c5829f153 100644 --- a/doc/src/sgml/ref/create_table_as.sgml +++ b/doc/src/sgml/ref/create_table_as.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_table_as.sgml,v 1.5 2001/03/03 22:11:40 tgl Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_table_as.sgml,v 1.6 2001/03/20 20:54:41 tgl Exp $ Postgres documentation --> @@ -15,7 +15,7 @@ Postgres documentation CREATE TABLE AS </refname> <refpurpose> - Creates a new table + Creates a new table from the results of a SELECT </refpurpose> </refnamediv> <refsynopsisdiv> @@ -41,7 +41,7 @@ CREATE [ TEMPORARY | TEMP ] TABLE <replaceable>table</replaceable> [ (<replaceab <term>TEMPORARY or TEMP</term> <listitem> <para> - If specified, the table is created only for this session, and is + If specified, the table is created only within this session, and is automatically dropped on session exit. Existing permanent tables with the same name are not visible (in this session) while the temporary table exists. @@ -55,7 +55,10 @@ CREATE [ TEMPORARY | TEMP ] TABLE <replaceable>table</replaceable> [ (<replaceab <term><replaceable>table</replaceable></term> <listitem> <para> - The name of a new table to be created. + The name of the new table to be created. + This table must not already exist. However, a temporary table + can be created that has the same name as an existing permanent + table. </para> </listitem> </varlistentry> @@ -76,8 +79,9 @@ CREATE [ TEMPORARY | TEMP ] TABLE <replaceable>table</replaceable> [ (<replaceab <term><replaceable>select_clause</replaceable></term> <listitem> <para> - A valid query statement. Refer to SELECT for a description of the - allowed syntax. + A valid query statement. Refer to + <xref linkend="sql-select" endterm="sql-select-title"> + for a description of the allowed syntax. </para> </listitem> </varlistentry> @@ -92,27 +96,47 @@ CREATE [ TEMPORARY | TEMP ] TABLE <replaceable>table</replaceable> [ (<replaceab <title> Outputs </title> + <para> - Refer to <command>CREATE TABLE</command> - and <command>SELECT</command> for a summary of possible output - messages. + Refer to + <xref linkend="sql-createtable" endterm="sql-createtable-title"> + and + <xref linkend="sql-select" endterm="sql-select-title"> + for a summary of possible output messages. </para> </refsect2> </refsynopsisdiv> <refsect1> <refsect1info> - <date>1998-09-22</date> + <date>2001-03-20</date> </refsect1info> <title> Description </title> <para> - <command>CREATE TABLE AS</command> enables a table to be created - from the contents of an existing table. - It is functionally equivalent to + <command>CREATE TABLE AS</command> creates a table and fills it + with data computed by a <command>SELECT</command> command. The + table columns have the names and datatypes associated with the + output columns of the <command>SELECT</command> (except that you + can override the <command>SELECT</command> column names by giving + an explicit list of column names). + </para> + + <para> + <command>CREATE TABLE AS</command> bears some resemblance to creating + a view, but it is really quite different: it creates a new table and + evaluates the <command>SELECT</command> just once to fill the new table + initially. The new table will not track subsequent changes to + the source tables of the <command>SELECT</command>. In contrast, + a view re-evaluates the given <command>SELECT</command> whenever queried. + </para> + + <para> + This command is functionally equivalent to <xref linkend="sql-selectinto" endterm="sql-selectinto-title">, - but with perhaps a more direct syntax. + but it is preferred since it is less likely to be confused with + other uses of the <command>SELECT ... INTO</command> syntax. </para> </refsect1> </refentry> diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml index 26bc9bdf4ef..f971359d8b2 100644 --- a/doc/src/sgml/ref/select.sgml +++ b/doc/src/sgml/ref/select.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.38 2001/02/04 12:18:08 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/select.sgml,v 1.39 2001/03/20 20:54:41 tgl Exp $ Postgres documentation --> @@ -15,7 +15,7 @@ Postgres documentation SELECT </refname> <refpurpose> - Retrieve rows from a table or view. + Retrieves rows from a table or view </refpurpose></refnamediv> <refsynopsisdiv> <refsynopsisdivinfo> @@ -24,7 +24,6 @@ Postgres documentation <synopsis> SELECT [ ALL | DISTINCT [ ON ( <replaceable class="PARAMETER">expression</replaceable> [, ...] ) ] ] * | <replaceable class="PARAMETER">expression</replaceable> [ AS <replaceable class="PARAMETER">output_name</replaceable> ] [, ...] - [ INTO [ TEMPORARY | TEMP ] [ TABLE ] <replaceable class="PARAMETER">new_table</replaceable> ] [ FROM <replaceable class="PARAMETER">from_item</replaceable> [, ...] ] [ WHERE <replaceable class="PARAMETER">condition</replaceable> ] [ GROUP BY <replaceable class="PARAMETER">expression</replaceable> [, ...] ] @@ -80,39 +79,6 @@ where <replaceable class="PARAMETER">from_item</replaceable> can be: </listitem> </varlistentry> - <varlistentry> - <term>TEMPORARY</term> - <term>TEMP</term> - <listitem> - <para> - If TEMPORARY or TEMP is specified, - the output table is created unique to this session, and is - automatically dropped on session exit. - </para> - </listitem> - </varlistentry> - - <varlistentry> - <term><replaceable class="PARAMETER">new_table</replaceable></term> - <listitem> - <para> - If the INTO TABLE clause is specified, the result of the - query will be stored in a new table with the indicated - name, rather than being returned to the client. - The target table (<replaceable class="PARAMETER">new_table</replaceable>) will - be created automatically and must not exist before this command. - Refer to <command>SELECT INTO</command> for more information. - - <note> - <para> - The <command>CREATE TABLE AS</command> statement will also - create a new table from a SELECT query. - </para> - </note> - </para> - </listitem> - </varlistentry> - <varlistentry> <term><replaceable class="PARAMETER">from_item</replaceable></term> <listitem> diff --git a/doc/src/sgml/ref/select_into.sgml b/doc/src/sgml/ref/select_into.sgml index c80395de803..50d2780a6dc 100644 --- a/doc/src/sgml/ref/select_into.sgml +++ b/doc/src/sgml/ref/select_into.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/select_into.sgml,v 1.9 2001/01/13 23:58:55 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/select_into.sgml,v 1.10 2001/03/20 20:54:41 tgl Exp $ Postgres documentation --> @@ -15,7 +15,7 @@ Postgres documentation SELECT INTO </refname> <refpurpose> - Create a new table from an existing table or view + Creates a new table from the results of a SELECT </refpurpose></refnamediv> <refsynopsisdiv> <refsynopsisdivinfo> @@ -48,51 +48,112 @@ where <replaceable class="PARAMETER">from_item</replaceable> can be: <refsect2 id="R2-SQL-SELECTINTO-1"> <refsect2info> - <date>1998-09-22</date> + <date>2001-03-20</date> </refsect2info> <title> Inputs </title> + + <para> + <variablelist> + <varlistentry> + <term>TEMPORARY</term> + <term>TEMP</term> + <listitem> + <para> + If TEMPORARY or TEMP is specified, + the output table is created only within this session, and is + automatically dropped on session exit. + Existing permanent tables with the same name are not visible + (in this session) while the temporary table exists. + Any indexes created on a temporary table are automatically + temporary as well. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><replaceable class="PARAMETER">new_table</replaceable></term> + <listitem> + <para> + The name of the new table to be created. + This table must not already exist. However, a temporary table + can be created that has the same name as an existing permanent + table. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + <para> - All input fields are described in detail for + All other inputs are described in detail for <xref linkend="sql-select" endterm="sql-select-title">. </para> </refsect2> <refsect2 id="R2-SQL-SELECTINTO-2"> <refsect2info> - <date>1998-09-22</date> + <date>2001-03-20</date> </refsect2info> <title> Outputs </title> + <para> - All output fields are described in detail for - <xref linkend="sql-select" endterm="sql-select-title">. + Refer to + <xref linkend="sql-createtable" endterm="sql-createtable-title"> + and + <xref linkend="sql-select" endterm="sql-select-title"> + for a summary of possible output messages. </para> </refsect2> </refsynopsisdiv> <refsect1 id="R1-SQL-SELECTINTO-1"> <refsect1info> - <date>1998-09-22</date> + <date>2001-03-20</date> </refsect1info> <title> Description </title> + <para> - <command>SELECT INTO</command> creates a new table from the results - of a query. Typically, this - query draws data from an existing table, but any SQL query is allowed. + <command>SELECT INTO</command> creates a new table and fills it + with data computed by a query. The data is not returned to the + client, as it is with a normal <command>SELECT</command>. The new + table's columns have the names and datatypes associated with the + output columns of the <command>SELECT</command>. <note> <para> <xref linkend="sql-createtableas" endterm="sql-createtableas-title"> - is functionally equivalent to the <command>SELECT INTO</command> command. + is functionally equivalent to <command>SELECT INTO</command>. + <command>CREATE TABLE AS</command> is the recommended syntax, since + <command>SELECT INTO</command> is not standard. In fact, this form of + <command>SELECT INTO</command> is not available in PL/pgSQL or ecpg, + because they interpret the INTO clause differently. </para> </note> </para> </refsect1> + + <refsect1 id="R1-SQL-SELECTINTO-2"> + <title> + Compatibility + </title> + + <para> + SQL92 uses <command>SELECT ... INTO</command> to represent selecting + values into scalar variables of a host program, rather than creating + a new table. This indeed is the usage found in PL/pgSQL and ecpg. + The <productname>Postgres</productname> usage of <command>SELECT + INTO</command> to represent table creation is historical. It's best + to use <command>CREATE TABLE AS</command> for this purpose in new code. + (<command>CREATE TABLE AS</command> isn't standard either, but it's + less likely to cause confusion.) + </para> + </refsect1> </refentry> <!-- Keep this comment at the end of the file |