Toán tử logic trong SQL

Bảng SINHVIEN có các bản ghi sau:

SQL> SELECT * FROM SINHVIEN;
+----+---------+-----+-----------+--------+
| ID |  TEN    | TUOI|  KHOAHOC  | HOCPHI |
+----+---------+-----+-----------+---------+
|  1 | Hoang   |  21 | CNTT      | 4       |
|  2 | Viet    |  19 | DTVT      | 3.0     |
|  3 | Thanh   |  18 | KTDN      |  4      |
|  4 | Nhan    |  19 | CK        |   4.5   |
|  5 | Huong   |  20 | TCNH      |   5     |
+----+---------+-----+-----------+---------+
5 rows in set (0.00 sec)

Dưới đây là các ví dụ minh họa cách sử dụng của các toán tử logic trong SQL:

SQL> SELECT * FROM SINHVIEN WHERE TUOI >= 19 AND HOCPHI >= 4;
+----+----------+-----+---------+---------+
| ID | TEN     | TUOI | KHOAHOC | HOCPHI  |
+----+----------+-----+---------+---------+
|  1 | Hoang   |  21 | CNTT      | 4       |
|  4 | Nhan    |  19 | CK        |   4.5   |
|  5 | Huong   |  20 | TCNH      |   5     |
+----+----------+-----+---------+---------+
3 rows in set (0.00 sec)


SQL> SELECT * FROM SINHVIEN WHERE TUOI >= 19 OR HOCPHI >= 4;
+----+----------+-----+-----------+----------+
| ID | TEN     | TUOI | KHOAHOC   | HOCPHI   |
+----+----------+-----+-----------+----------+
|  1 | Hoang   |  21 | CNTT      | 4       |
|  3 | Thanh   |  18 | KTDN      |  4      |
|  4 | Nhan    |  19 | CK        |   4.5   |
|  5 | Huong   |  20 | TCNH      |   5     |
+----+----------+-----+-----------+----------+
4 rows in set (0.00 sec)

SQL>  SELECT * FROM SINHVIEN WHERE TUOI IS NOT NULL;
+----+----------+-----+-----------+----------+
| ID | TEN     | TUOI | KHOAHOC   | HOCPHI   |
+----+----------+-----+-----------+----------+
|  1 | Hoang   |  21 | CNTT      | 4       |
|  2 | Viet    |  19 | DTVT      | 3.0     |
|  3 | Thanh   |  18 | KTDN      |  4      |
|  4 | Nhan    |  19 | CK        |   4.5   |
|  5 | Huong   |  20 | TCNH      |   5     |
+----+----------+-----+-----------+----------+
5 rows in set (0.00 sec)

SQL> SELECT * FROM SINHVIEN WHERE TEN LIKE 'Hu%';
+----+-------+-----+---------+---------+
| ID | TEN  | TUOI | KHOAHOC | HOCPHI  |
+----+-------+-----+---------+---------+
|  5 | Huong   |  20 | TCNH      |   5     |
+----+-------+-----+---------+---------+
1 row in set (0.00 sec)

SQL> SELECT * FROM SINHVIEN WHERE TUOI IN ( 20, 21 );
+----+----------+-----+---------+---------+
| ID | TEN     | TUOI | KHOAHOC | HOCPHI  |
+----+----------+-----+---------+---------+
|  1 | Hoang   |  21 | CNTT      | 4       |
|  5 | Huong   |  20 | TCNH      |   5     |
+----+----------+-----+---------+---------+
2 rows in set (0.00 sec)

SQL> SELECT * FROM SINHVIEN WHERE TUOI BETWEEN 20 AND 21;
+----+----------+-----+---------+---------+
| ID | TEN     | TUOI | KHOAHOC | HOCPHI  |
+----+----------+-----+---------+---------+
|  1 | Hoang   |  21 | CNTT      | 4       |
|  5 | Huong   |  20 | TCNH      |   5     |
+----+----------+-----+---------+---------+
2 rows in set (0.00 sec)