UNION 操作
语法:SELECT * FROM 表名1 UNION ALL SELECT * FROM 表名2
UNION 操作要保证两个表或者多个表的列数要相同(看列子)
例子:SELECT * FROM student UNION ALL SELECT * FROM Course
UNION 操作
语法:SELECT * FROM 表名1 UNION ALL SELECT * FROM 表名2
UNION 操作要保证两个表或者多个表的列数要相同(看列子)
例子:SELECT * FROM student UNION ALL SELECT * FROM Course