diff options
Diffstat (limited to 'doc/src/sgml/queries.sgml')
| -rw-r--r-- | doc/src/sgml/queries.sgml | 25 |
1 files changed, 14 insertions, 11 deletions
diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml index e65dbb4c2f9..99c4e4e6989 100644 --- a/doc/src/sgml/queries.sgml +++ b/doc/src/sgml/queries.sgml @@ -895,16 +895,16 @@ SELECT product_id, p.name, (sum(s.units) * p.price) AS sales all sales of the product. </para> + <indexterm><primary>functional dependency</primary></indexterm> + <para> - If the products table is set up so that, - say, <literal>product_id</literal> is the primary key, then it - would be enough to group by <literal>product_id</literal> in the - above example, since name and price would - be <firstterm>functionally - dependent</firstterm><indexterm><primary>functional - dependency</primary></indexterm> on the product ID, and so there - would be no ambiguity about which name and price value to return - for each product ID group. + If the products table is set up so that, say, + <literal>product_id</literal> is the primary key, then it would be + enough to group by <literal>product_id</literal> in the above example, + since name and price would be <firstterm>functionally + dependent</firstterm> on the product ID, and so there would be no + ambiguity about which name and price value to return for each product + ID group. </para> <para> @@ -1170,9 +1170,12 @@ SELECT DISTINCT <replaceable>select_list</replaceable> ... can be used to specify the default behavior of retaining all rows.) </para> + <indexterm> + <primary>null value</> + <secondary sortas="DISTINCT">in DISTINCT</> + </indexterm> + <para> - <indexterm><primary>null value</><secondary sortas="DISTINCT">in - DISTINCT</></indexterm> Obviously, two rows are considered distinct if they differ in at least one column value. Null values are considered equal in this comparison. |