union and union all in sql server
/* UNION AND UNION ALL*/
union and union all operator in sql server are used to combine the result-set of
two or more select queries.
union remove duplicate rows, where as union all doesn't.
.e.g_
SELECT Column_List from Table_Name
UNION
SELECT Column_List from Table_Name
/--------------------------------------------/
.e.g_
SELECT Column_List from Table_Name
UNION ALL
SELECT Column_List from Table_Name
/* UNION AND JOIN */
Union combine rows from 2 or more tables, where as
join combine columns from 2 or more tables.