diff options
| -rw-r--r-- | doc/src/sgml/ref/copy.sgml | 6 | ||||
| -rw-r--r-- | doc/src/sgml/ref/select.sgml | 39 |
2 files changed, 33 insertions, 12 deletions
diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml index 006b0224121..39eeec38e4f 100644 --- a/doc/src/sgml/ref/copy.sgml +++ b/doc/src/sgml/ref/copy.sgml @@ -395,7 +395,11 @@ has the termination sequence on the last line): </refsect1> <refsect1 ID="R1-SQL-COPY-5"> - <title>Bugs</title> + <title>Bugs and features</title> + <para> + <command>COPY</command> neither invokes rules nor acts on column defaults. + It does invoke triggers, however. + </para> <para> <command>COPY</command> stops operation at the first error. This should not lead to problems in the event of diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml index 6306b490e3b..bf44ee9c3f5 100644 --- a/doc/src/sgml/ref/select.sgml +++ b/doc/src/sgml/ref/select.sgml @@ -205,9 +205,15 @@ SELECT [ALL|DISTINCT [ON <replaceable class="PARAMETER">column</replaceable>] ] Description </title> <para> - <command>SELECT</command> will get all rows which satisfy the - WHERE condition - or all rows of a table if WHERE is omitted.</para> + <command>SELECT</command> will return rows from one or more tables. + Candidates for selection are rows which satisfy the WHERE condition; + if WHERE is omitted, all rows are candidates.</para> + <para> + <command>DISTINCT</command> will eliminate all duplicate rows from the + selection. + <command>DISTINCT ON <replaceable class="PARAMETER">column</replaceable></command> will eliminate all duplicates in the specified column; this is +equivalent to using <command>GROUP BY <replaceable class="PARAMETER">column</replaceable></command>. <command>ALL</command> will return all candidate rows, +including duplicates. <para> The GROUP BY clause allows a user to divide a table @@ -247,8 +253,9 @@ WHERE <replaceable class="PARAMETER">expr</replaceable> <replaceable class="PARA </synopsis> where <replaceable class="PARAMETER">cond_op</replaceable> can be - one of: =, <, <=, >, >=, <> - or a conditional operator like ALL, ANY, IN, LIKE, et cetera + one of: =, <, <=, >, >= or <>, + a conditional operator like ALL, ANY, IN, LIKE, et cetera or a + locally-defined operator, and <replaceable class="PARAMETER">log_op</replaceable> can be one of: AND, OR, NOT. The comparison returns either TRUE or FALSE and all @@ -266,10 +273,16 @@ WHERE <replaceable class="PARAMETER">expr</replaceable> <replaceable class="PARA </title> <para> GROUP BY specifies a grouped table derived by the application - of the this clause: + of this clause: <synopsis> GROUP BY <replaceable class="PARAMETER">column</replaceable> [, ...] - </synopsis></para></refsect2> + </synopsis></para> + <para> + GROUP BY will condense into a single row all rows that share the same values for the + grouped columns; aggregates return values derived from all rows that make up the group. The value returned for an ungrouped + and unaggregated column is dependent on the order in which rows happen to be read from the database. + </para> +</refsect2> <refsect2 id="R2-SQL-HAVING-2"> <refsect2info> @@ -327,8 +340,8 @@ SELECT title, date_prod + 1 AS newlen FROM films ORDER BY newlen; </programlisting></para> <para> - The columns in the ORDER BY must appear in the SELECT clause. - Thus the following statement is illegal: + From release 6.4 of PostgreSQL, the columns in the ORDER BY clause do not need to appear in the SELECT clause. + Thus the following statement is now legal: <programlisting> SELECT name FROM distributors ORDER BY code; </programlisting></para> @@ -409,7 +422,7 @@ SELECT f.title, f.did, d.name, f.date_prod, f.kind </programlisting> <para> To sum the column <literal>len</literal> of all films and group - the reults by <literal>kind</literal>: + the results by <literal>kind</literal>: </para> <programlisting> SELECT kind, SUM(len) AS total FROM films GROUP BY kind; @@ -425,7 +438,7 @@ SELECT kind, SUM(len) AS total FROM films GROUP BY kind; <para> To sum the column <literal>len</literal> of all films, group - the reults by <literal>kind</literal> and show those group totals + the results by <literal>kind</literal> and show those group totals that are less than 5 hours: </para> <programlisting> @@ -563,6 +576,10 @@ SELECT distributors.* WHERE name = 'Westwood'; This is not currently allowed in <productname>Postgres</productname>. </para> + + <para> + The DISTINCT ON phrase is not part of <acronym>SQL92</acronym>. + </para> </refsect3> <refsect3 id="R3-SQL-UNION-1"> |