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"GROUP BY" - Dividing Query Output into Multiple Groups in SQL Server
How To Divide Query Output into Multiple Groups with the GROUP BY Clause in SQL Server?
✍: FYIcenter.com
Sometimes, you want to divide the query output into multiple groups, and apply group functions on each individual groups. Dividing query output into multiple groups can be done with the GROUP BY clause. Here is the syntax of a SELECT statement with a GROUP BY clause.
SELECT group_level_fields FROM source_tables WHERE search_condition GROUP BY group_by_expression
The final output of the SELECT statement is the resulting values of group_level_fields for each group.
The following script gives you a good GROUP BY example with a single column as the group_by_expression. In this case, rows with the same value of this column will be considered as a single group.
SELECT tag, COUNT(*), MAX(counts), MIN(created) FROM fyi_links GROUP BY tag GO tag COUNT(*) MAX(counts) MIN(created) DBA 3 972 2005-01-01 DEV 2 439 2004-01-01 SQA 2 828 2003-01-01
Notice that, column "tag" can also be used in group_level_fields, because it is used as the group_by_expression, and becomes a constant for any given group.
⇒ HAVING - Apply Filtering Criteria at Group Level in SQL Server
⇐ Mixing Group Functions with Non-group Selection Fields in SQL Server
⇑ Using SELECT Statements and GROUP BY Clauses in SQL Server
2016-10-25, 3003🔥, 0💬
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