Comments on: INSERT ON DUPLICATE KEY UPDATE and REPLACE INTO

By: Jeff

Jeff — Fri, 04 Sep 2009 20:42:49 +0000

One benefit of REPLACE over UPDATE is the DELAYED feature, which comes in handy.

By: Possible improvement with caches | reexport

Possible improvement with caches | reexport — Sun, 13 Jul 2008 15:55:47 +0000

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By: G Barnes

G Barnes — Sun, 13 Apr 2008 15:46:03 +0000

I have two identical tables named Table1 and Table2 on two computers respectivaly. There are two fields in each, “ITEM” and “SOLD”. In both tables, “ITEM” is the primary key. Is there a way to merge Table1 into Table2 with something similar to INSERT ON DUPLICATE UPDATE sold =sold +(the first table’s sold value)? Thus if Table1 contains 10 (in the sold field) and Table2 contains 20. I want the total in Table 2 to be 30. Is this possible?

By: P.ANBALAGAN

P.ANBALAGAN — Mon, 10 Mar 2008 07:14:41 +0000

I WANT QUERY FOR TO INSERT MORE 100000 RECORDS IN A TABLE.

By: Jonathan Haddad

Jonathan Haddad — Wed, 07 Feb 2007 19:03:12 +0000

Jerry:
Thanks for the tip – I’ll be sure to keep that in mind. For the most part, in what I do, INSERT ON DUPLICATE UPDATE is what I need to use, especially knowing the cascading keys issue.

By: John Ventimiglia

John Ventimiglia — Wed, 31 Jan 2007 15:02:12 +0000

Also related to Jerrys comments, REPLACE will use the next available # on auto-increment fields, which may not always be desired.

By: peter

peter — Tue, 23 Jan 2007 01:24:47 +0000

Thanks Jerry,

Good catch.

By: Jerry Zheng

Jerry Zheng — Tue, 23 Jan 2007 01:16:23 +0000

Here is a test case:

mysql> select version();
+———————+
| version() |
+———————+
| 4.1.18-standard-log |
+———————+

mysql> create table p(id int primary key, notid int) type=innodb;
Query OK, 0 rows affected, 1 warning (0.07 sec)

mysql> create table c (id int primary key, fk int , foreign key (fk) references p(id) on delete CASCADE ) type=innodb;
Query OK, 0 rows affected, 1 warning (0.06 sec)

mysql> insert into p values (1,1), (2,2);
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0

mysql> insert into c values (1,1), (2,2);
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0

mysql> select * from p;
+—-+——-+
| id | notid |
+—-+——-+
| 1 | 1 |
| 2 | 2 |
+—-+——-+
2 rows in set (0.00 sec)

mysql> select * from c;
+—-+——+
| id | fk |
+—-+——+
| 1 | 1 |
| 2 | 2 |
+—-+——+
2 rows in set (0.00 sec)

mysql> replace into p values (1,10);
Query OK, 2 rows affected (0.00 sec)

mysql> select * from c;
+—-+——+
| id | fk |
+—-+——+
| 2 | 2 |
+—-+——+
1 row in set (0.00 sec)

– We lost the child #1.

mysql> insert into p (id, notid) values (2,20) on duplicate key update notid=20;
Query OK, 2 rows affected (0.01 sec)

mysql> select * from c;
+—-+——+
| id | fk |
+—-+——+
| 2 | 2 |
+—-+——+
1 row in set (0.00 sec)

– Child #2 is safe.

mysql> select * from p;
+—-+——-+
| id | notid |
+—-+——-+
| 1 | 10 |
| 2 | 20 |
+—-+——-+
2 rows in set (0.00 sec)

By: Jerry Zheng

Jerry Zheng — Tue, 23 Jan 2007 01:07:12 +0000

The two statements have different impact for INNODb table.
The REPLACE INTO acts as DELETE/INSERT for duplicates.
The INSERT ON DUPLIACTE UPDATE is true update.

If you have a child table defined with “on delete CASCADE”, the REPLACE INTO will delete the child record too.

I will use INSERT ON DUPLICATE rather than the REPLACE INTO for the above reason.

By: peter

peter — Thu, 18 Jan 2007 20:11:17 +0000

Sure,

I do not have benchmarks with Innodb but I’d expect them to be close. I’d mostly look at what makes more sense for your application from development standpoint.