Union and Union all

SQL Union operator

The Union operator is used to merge the result sets of two or more select statements.

Note that the SELECT statement inside the Union must have the same number of columns. Columns must also have similar data types. In addition, the columns in each select statement must be in the same order.

SQL Union syntax (exclude duplicate data)

select * from stuunionselect * from stu

SQL Union all syntax (repeated data is not excluded)

select * from stuunion allselect * from stu

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Union and Union all