SQL UNION
The UNION operator is used to combine the result-set of two or more SELECT
statements.
- Each SELECT statement within UNION must have the same number
of columns
- The columns must also have similar data types
- The columns in
each SELECT statement must also be in the same order
UNION Syntax
SELECT column_name(s) FROM table1
UNION
SELECT column_name(s) FROM table2;
UNION ALL Syntax
The UNION operator selects only distinct values by default. To allow
duplicate values, use UNION ALL:
SELECT column_name(s) FROM table1
UNION ALL
SELECT column_name(s) FROM table2;
