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SQL-J Language Reference
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Reference Manual |
SUMSUM is an aggregate expression that evaluates the sum of the expression over a set of rows (see Aggregates (Set Functions)). SUM is allowed only on expressions that evaluate to numeric data types. SyntaxSUM ( [ DISTINCT | ALL ] Expression ) The DISTINCT and ALL qualifiers eliminate or retain duplicates. ALL is assumed if neither ALL nor DISTINCT is specified. For example, if a column contains the values 1, 1, 1, 1, and 2, SUM(col) returns a greater value than COUNT(DISTINCT col). Only one DISTINCT aggregate expression per SelectExpression is allowed. For example, the following query is not allowed:
SELECT AVG (DISTINCT flying_time), SUM (DISTINCT miles) The Expression can contain multiple column references or expressions, but it cannot contain another aggregate or subquery. It must evaluate to a built-in numeric data type or to a Java data type that is automatically mapped to a built-in numeric data type. You can therefore call methods that evaluate to built-in data types. (For example, a method that returns a java.lang.Integer or int evaluates to an INTEGER.) If an expression evaluates to NULL, the aggregate skips that value. The resulting data type is the same as the expression on which it operates (it may overflow). SUM Examples
-- find all the rooms booked
-- use SUM on a method invocation
-- use SUM on multiple column references |
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