CODEWITHSUNDEEP
mysqlsql
devJackie
devJackie

Reputation: 119

Mysql - count it works without groupby clause

I'm confused with count aggregation function.

Below sentence is mysql and it worked without a groupby clause. how could it be possible?

SELECT
        COUNT(1) AS cnt
FROM    dual;

result : 1

Is there any parameter that groupby clause is default when count aggregation function called.

help me out plz.

Upvotes: 1

Views: 56

Answers (1)

Gordon Linoff
Gordon Linoff

Reputation: 1269643

Aggregation functions such as COUNT(), SUM() and AVG() are used in aggregation queries. Such queries calculate the values based on groups of rows that are summarized into a single row in the result set.

Normally, an aggregation query uses a GROUP BY to define the rows in the result set. The result set has one row for each unique combination of the GROUP BY keys found in the data.

When such a query does not have a GROUP BY, then the entire table is considered a group and it is summarized into exactly one row. Incidentally, this is true even when there are no rows in the table. The result would be a count of 0.

Upvotes: 7

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