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Diffstat (limited to 'doc/src/sgml/sql.sgml')
| -rw-r--r-- | doc/src/sgml/sql.sgml | 24 |
1 files changed, 12 insertions, 12 deletions
diff --git a/doc/src/sgml/sql.sgml b/doc/src/sgml/sql.sgml index b27400b4a45..d8b2934063d 100644 --- a/doc/src/sgml/sql.sgml +++ b/doc/src/sgml/sql.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/sql.sgml,v 1.40 2006/04/30 18:30:38 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/sql.sgml,v 1.41 2006/07/27 19:52:04 tgl Exp $ --> <chapter id="sql-intro"> <title>SQL</title> @@ -1247,13 +1247,13 @@ select sname, pname from supplier </sect3> <sect3> - <title id="aggregates-tutorial">Aggregate Operators</title> + <title id="aggregates-tutorial">Aggregate Functions</title> <para> - <acronym>SQL</acronym> provides aggregate operators (e.g. AVG, - COUNT, SUM, MIN, MAX) that take an expression as argument. The - expression is evaluated at each row that satisfies the WHERE - clause, and the aggregate operator is calculated over this set + <acronym>SQL</acronym> provides aggregate functions such as AVG, + COUNT, SUM, MIN, and MAX. The argument(s) of an aggregate function + are evaluated at each row that satisfies the WHERE + clause, and the aggregate function is calculated over this set of input values. Normally, an aggregate delivers a single result for a whole <command>SELECT</command> statement. But if grouping is specified in the query, then a separate calculation @@ -1311,10 +1311,10 @@ SELECT COUNT(PNO) <para> <acronym>SQL</acronym> allows one to partition the tuples of a table into groups. Then the - aggregate operators described above can be applied to the groups — - i.e. the value of the aggregate operator is no longer calculated over + aggregate functions described above can be applied to the groups — + i.e. the value of the aggregate function is no longer calculated over all the values of the specified column but over all values of a - group. Thus the aggregate operator is evaluated separately for every + group. Thus the aggregate function is evaluated separately for every group. </para> @@ -1396,7 +1396,7 @@ SELECT S.SNO, S.SNAME, COUNT(SE.PNO) <para> In our example we got four groups and now we can apply the aggregate - operator COUNT to every group leading to the final result of the query + function COUNT to every group leading to the final result of the query given above. </para> </example> @@ -1404,9 +1404,9 @@ SELECT S.SNO, S.SNAME, COUNT(SE.PNO) <para> Note that for a query using GROUP BY and aggregate - operators to make sense the target list can only refer directly to + functions to make sense, the target list can only refer directly to the attributes being grouped by. Other attributes may only be used - inside the argument of an aggregate function. Otherwise there would + inside the arguments of aggregate functions. Otherwise there would not be a unique value to associate with the other attributes. </para> |