MySQL Union and UNION ALL

The UNION operator is used to combine the result set of two or more SELECT statements. The SELECT statement inside the UNION must have the same number of columns. The column must also have a similar data type. The Union is to set the data together, excluding duplicate rows, while making the default sort usage:

SELECT  from table_name1 UNION SELECT  from Table_name2

Union All is an assembly operation on the data, including repeating rows, without ordering usage:

SELECT  from table_name1 UNION  All SELECT  from Table_name2

MySQL Union and UNION ALL