CodePudding user response:

First SELECT "', no column name, your query result is not the result of the second SELECT, is the first

CodePudding user response:

Girl watches the union boy

CodePudding user response:

Will be subject to the first column to Select, Select can not write a column name

CodePudding user response:

After the first select statement 'fields to add a AS the column name (individual), the UNION was named after the first select field