Aggregators

Aggregators

SQL Standard

• SUM()
• AVG()
• COUNT()
• MAX()
• MIN()
• FIRST()
• LAST()

Examples:

    SELECT COUNT()
    SELECT COUNT(one)
    SELECT COUNT(*)

Non-standard

• AGGR() – operations on aggregated values
• ARRAY() – create array of values
• User-defined aggregators

Example of AGGR() aggregator (here avg1 = avg2)

    SELECT SUM(a) AS sm, COUNT(*) AS cnt, \
           AGGR(sm/cnt) AS avg1, AVG(a) AS avg2 FROM data