Oracle set union, union all, intersect, minus

The efficiency of oracle union, union all, intersect, and minus oracle integration is higher than that of normal ones. Test Case -- test table data www.2cto.com SQL> select stuid from zr_stu; STUID ----------- 1 2 3 4 5 6 7 7 rows selected Executed in 0.14 seconds -- table data SQL> select stuid from zr_stu where stuid> 3; STUID ----------- 4 5 6 7 www.2cto.com Executed in 0.047 seconds SQL> select stuid from zr_stu where stuid <6; STUID ----------- 1 2 3 4 5 Executed in 0.109 seconds -- union www.2cto.com SQL> select stuid from zr_stu where stuid> 4 union select stuid from zr_stu where stuid <6; STUID ---------- 1 2 3 4 5 6 7 7 rows selected Executed in 0.031 seconds -- union all SQL> select stuid from zr_stu where stuid> 4 2 union all 3 select stuid from zr_stu where stuid <6; STUID ---------- 5 6 7 1 2 3 4 5 www.2cto.com 8 rows selected Executed in 0.156 seconds -- intersect SQL> select stuid from zr_stu where stuid> 4 2 intersect 3 select stuid from zr_stu where stuid <6; STUID ---------- 5 Executed in 0.078 seconds www.2cto.com -- minus SQL> select stuid from zr_stu where stuid> 4 2 minus 3 select stuid from zr_stu where stuid <6; STUID ---------- 6 7 Executed in 0.062 seconds