Shulou(Shulou.com)06/01 Report--

Complete grammar

Simple query

Filter conditions before grouping in where

Group by grouping

What is grouping: categorized according to the same parts of all records, certain fields with low discrimination

Why grouping: when we want to count on a group basis, we have to group.

The purpose of grouping is to make statistics on a group basis, and then to consider that a single record is meaningless.

Aggregate function

Usage

Having is further screened for the results of the aggregation after the aggregation.

Order by sorting

Conditions under which limit restricts display

Regular expression

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