latihan lock
DESCRIPTION
Latihan Lock. Transaksi. - BEGIN transaksi COMMIT; - ROLLBACK; (utk membatalkan). Transaksi. buatlah tabel rekening dan isikan datanya CREATE TABLE rekening ( norek char (10) PRIMARY KEY, nama varchar (30) , saldo numeric (10.2) ) ; DESCRIBE mhs ; - PowerPoint PPT PresentationTRANSCRIPT
Latihan Lock
Transaksi
- BEGIN transaksi COMMIT;
- ROLLBACK; (utk membatalkan)
Transaksi
• buatlah tabel rekening dan isikan datanyaCREATE TABLE rekening (norek char(10) PRIMARY KEY, nama varchar(30), saldo numeric(10.2));DESCRIBE mhs;INSERT INTO rekening VALUES (‘111’,’Bapak’,5000000);
INSERT INTO rekening VALUES (‘222’,’anak’,1000000);SELECT * FROM rekening;
• buatlah transaksi transfer uang 1 juta dari Bapak ke anak
Transaksi
Jawaban:BEGIN;BEGIN;UPDATE rekening SET saldo=saldo-1000000 WHERE
nama=‘Bapak’;UPDATE rekening SET saldo=saldo+1000000 WHERE nama=‘anak’; COMMIT;
Latihan:BEGIN;UPDATE rekening SET saldo=saldo-1000000 WHERE
nama=‘Bapak’;ROLLBACK;
A
• mysql> CREATE TABLE t (i INT) ENGINE = InnoDB; Query OK, 0 rows affected (1.07 sec)
• mysql> INSERT INTO t (i) VALUES(1); Query OK, 1 row affected (0.09 sec)
• mysql> START TRANSACTION; Query OK, 0 rows affected (0.00 sec)
• mysql> SELECT * FROM t WHERE i = 1 LOCK IN SHARE MODE; 1 row in set (0.10 sec)
B
• mysql> START TRANSACTION; Query OK, 0 rows affected (0.00 sec)
• mysql> DELETE FROM t WHERE i = 1;
A
• mysql> DELETE FROM t WHERE i = 1; ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction
Sama-sama minta exclusive lock jadi deadlock
Consistent Read
A
• mysql> BEGIN; Query OK, 0 rows affected (0.00 sec)
• mysql> SELECT MAX(i) FROM t;
• mysql> INSERT INTO t(i) VALUES (4); Query OK, 1 row affected (0.00 sec)
B
• mysql> BEGIN; Query OK, 0 rows affected (0.00 sec)
• mysql> SELECT MAX(i) FROM t;
• mysql> INSERT INTO t(i) VALUES(4); Query OK, 1 row affected (0.00 sec)
• mysql> COMMIT; Query OK, 0 rows affected (0.00 sec)
A
• mysql> COMMIT; Query OK, 0 rows affected (0.00 sec)
• mysql> SELECT * FROM t;
A
• mysql> DELETE FROM t WHERE i=4; Query OK, 2 rows affected (0.00 sec)
• mysql> SELECT * FROM t;
A
• mysql> SELECT * FROM t;
• mysql> BEGIN; Query OK, 0 rows affected (0.00 sec)
• mysql> SELECT MAX(i) FROM t FOR UPDATE;
• mysql> INSERT INTO t(i) VALUES (4); Query OK, 1 row affected (0.00 sec)
B
• mysql> SELECT MAX(i) FROM t FOR UPDATE;
• mysql> COMMIT; Query OK, 0 rows affected (0.00 sec)
B
• mysql> SELECT MAX(i) FROM t FOR UPDATE;
• mysql> INSERT INTO t(i) VALUES(5); Query OK, 1 row affected (0.00 sec)
• mysql> COMMIT; Query OK, 0 rows affected (0.01 sec)
• mysql> SELECT * FROM t;
READ LOCK A
• mysql> BEGIN; Query OK, 0 rows affected (0.00 sec)
• mysql> SELECT MAX(i) FROM t LOCK IN SHARE MODE;
B
• mysql> UPDATE t SET i = 55 WHERE i=5;
A
• mysql> COMMIT; Query OK, 0 rows affected (0.00 sec)
B
• mysql> UPDATE t SET i = 55 WHERE i=5; Query OK, 0 rows affected (6.95 sec) Rows matched: 0 Changed: 0 Warnings: 0
• mysql> UPDATE t SET i = 55 WHERE i=5; Query OK, 1 row affected (43.30 sec) Rows matched: 1 Changed: 1 Warnings: 0
• mysql> SELECT * FROM t;