Group in SqlServer

1. Groupby can merge the same data into a group, and the grouped data can be considered as a temporary table. Note that if the SQL statement contains the where condition, the groupby must be placed after the where clause. 2. You can specify multiple columns in the group by clause. You only need to separate the column names of multiple columns with commas. After multiple grouping rules are specified, the database system

1. Group by can merge the same data into a group. The grouped data can be considered as a temporary table. Note that if SQL has the where condition, Group by must be placed after where. 2. You can specify multiple columns in the group by clause. You only need to separate the column names of multiple columns with commas. After multiple grouping rules are specified, the database system

1. group by can combine the same data into a Group of US space. The grouped data can be considered as a temporary table. Note that if SQL has the where condition, the Hong Kong virtual host, group by must be placed after where. 2. You can specify multiple columns in the group by clause. You only need to separate the column names of multiple columns with commas. Multiple groups
After the rules are met, the VM and database system group the data layer by layer according to the defined grouping order.
Group rows, and then group again in each group according to the second grouping column ...... Group layer by layer to implement "group in group"
The query result set is output by the last-level grouping. 3. After grouping, you can also collect statistics on the group data. This is an aggregate function. 4. order by is used to sort the grouped data. 5. Sometimes we need to filter the statistical results after grouping. This is to use the having keyword to filter the statistical results.