4.2.3 Aggregate expressions

Aggregate expressions ( <aggr_expr>s) are currently used exclusively by the LOGS statement. They represent an expression with a given function applied to the aggregate of all (dynamic) instances of that expression. <aggr_expr>s take one of four forms:

(In the above, <expr> refers to an arithmetic expression defined in Arithmetic expressions and <aggr_func> refers to one of the functions defined in Aggregate functions.)

The first form does not summarize <expr>; every individual instance of <expr> is utilized. The second form asserts that <expr> is a constant (i.e., all values are identical) and utilizes that constant.¹³ The third form applies each <aggr_func> to the set of all values of <expr> and utilizes the result of that function. The fourth form produces a histogram of all values of <expr>, i.e., a list of {unique value, tally} pairs, sorted by unique value.