Of the Latest MySQL, Syntax Presented in the Title is Not Possible

8/9/2019 Of the Latest MySQL, Syntax Presented in the Title is Not Possible

1/15

MySQL: INSERT IF NOT EXISTS syntax

18th October 2007

To start: as of the latest MySQL, syntax presented in the title is not possible. But there are several veryeasy ways to accomplish what is expected using existing functionality.

There are 3 possible solutions: using INSERT IGNORE, REPLACE, or INSERT ... ON DUPLICATEKEY UPDATE.

Imagine we have a table:

PLAIN TEXTSQL:

1.CREATE TABLE `transcripts` (

2.

ènsembl_transcript_id` varchar(20) NOT NULL,3.

`transcript_chrom_start` int(10) UNSIGNED NOT NULL,

4.`transcript_chrom_end` int(10) UNSIGNED NOT NULL,

5.

PRIMARY KEY (ènsembl_transcript_id`)

6.) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Now imagine that we have an automatic pipeline importing transcripts meta-data from Ensembl, andthat due to various reasons the pipeline might be broken at any step of execution. Thus, we need to

ensure two things: 1) repeated executions of the pipeline will not destroy our database, and 2) repeated

executions will not die due to 'duplicate primary key' errors.

Method 1: using REPLACE

It's very simple:PLAIN TEXT

SQL:

1.

REPLACE INTO `transcripts`

2.SET ènsembl_transcript_id` = 'ENSORGT00000000001',

3.

`transcript_chrom_start` = 12345,4.

`transcript_chrom_end` = 12678;


2/15

If the record exists, it will be overwritten; if it does not yet exist, it will be created.

However, using this method isn't efficient for our case: we do not need to overwrite existing records,

it's fine just to skip them.

Method 2: using INSERT IGNORE

Also very simple:

PLAIN TEXTSQL:

1.INSERT IGNORE INTO `transcripts`

2.

SET `ensembl_transcript_id` = 'ENSORGT00000000001',

3.`transcript_chrom_start` = 12345,

4.

`transcript_chrom_end` = 12678;

Here, if the 'ensembl_transcript_id' is already present in the database, it will be silently skipped

(ignored). (To be more precise, here's a quote from MySQL reference manual: "If you use the IGNOREkeyword, errors that occur while executing the INSERT statement are treated as warnings instead. For

example, without IGNORE, a row that duplicates an existing UNIQUE index or PRIMARY KEY value

in the table causes a duplicate-key error and the statement is aborted.".) If the record doesn't yet exist, itwill be created.

This second method has several potential weaknesses, including non-abortion of the query in case any

other problem occurs (see the manual). Thus it should be used if previously tested without theIGNORE keyword.

There is one more option: to use INSERT ... ON DUPLICATE KEY UPDATE syntax, and in theUPDATE part just do nothing do some meaningless (empty) operation, like calculating 0+0 (Geoffray

suggests doing the id=id assignment for the MySQL optimization engine to ignore this operation).

Advantage of this method is that it only ignores duplicate key events, and still aborts on other errors.

As a final notice: this post was inspired by Xaprb. I'd also advise to consult his other post on writing

flexible SQL queries.

* Delicious

* Google Bookmarks

* Yahoo Bookmarks* Windows Live Favorites

* Technorati Favorites

* Digg* Slashdot

* StumbleUpon

Read It Later


3/15

mayor

abram

fatalaiya* Twitter* Share/BookmarkThis entry was posted on Thursday, October 18th, 2007 at 15:20 and is filed under Programming. Youcan follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackbackfrom your own site.28 Responses to MySQL: INSERT IF NOT EXISTS syntax

1. MYSQL On Duplicate Key Do Nothing OR Insert If Not Exists Says:

April 20th, 2008 at 8:19

[...] may also find http://bogdan.org.ua/2007/10/18/mysql-insert-if-not-exists-syntax.html good

reading on the [...]2. ceteras Says:

June 23rd, 2008 at 14:09

Very interesting, and helpful.

3. Bogdan Says:


4/15

June 24th, 2008 at 9:34

mayor

abram

fatalaiyathanks :)4. Tautvydas Says:July 13th, 2008 at 12:53Thanks!

5. Emir Bugra KOKSALAN Says:

July 22nd, 2008 at 12:38

Thank you very much!!6. Teo Says:

August 4th, 2008 at 13:41

Very useful, thank you! How about insert, update and delete in a single query, it's possible?

Something like:

insert ignore into table (field_one, field_two) values (values_one, values_two) on duplicate key

update field_one = values(values_one), field_two = values(values_two) THEN QUERY FOR DELETE


5/15

HERE?

Thanks

7. Bogdan Says:August 4th, 2008 at 19:25


6/15


7/15


8/15

Teo,


9/15

As I didn't do anything similar before, I can't offer you a ready working solution.

But you should just try your query :) . The part before THEN should work (unless "insert ignore" is

not compatible with "on duplicate key"). For THEN-part, I suspect different syntax might be needed -look for MySQL conditional statements IF-THEN-ELSE.

8. Geoffray Says:

August 28th, 2008 at 14:39

About your last option, I don't think it's possible to do nothing after the "ON DUPLICATE KEY

UPDATE". What you can do is updating the column (PRIMARY KEY or/and UNIQUE) whichgenerate a duplicate entry error with it's own value. I think MySQL will ignore the update because

these values are similar, so it could also be a quite fast solution.

INSERT INTO `test`(id) VALUES (1) ON DUPLICATE KEY UPDATE id=id9. Bogdan Says:

August 30th, 2008 at 16:21

Geoffray,

if the MySQL optimization engine really does that, and if this is allowed (remember, we aretriggering the ON DUPLICATE KEY event, and then trying to assign that key's value to another value,

even if it is the same), then this is a really good solution.

Based on your comment, I updated the post, as MySQL syntax in fact doesn't allow the empty

statement after ON (...) UPDATE.

10. Marius Says:

September 29th, 2008 at 16:04

Would this work on InnoDB with composite keys as well? My task is to read only new entries from

a log and insert them into a MySQL table. The table has a composite key.

(I could try this myself, but I have no MySQL box to test on for the next few weeks.)

11. Bogdan Says:September 29th, 2008 at 21:55

Marius,

neither MySQL documentation, nor my (not so extensive) experience with MySQL raise any

support for disabling described functionality for composite keys. As I understand, composite key is still

a single key, and behaves as such. And MySQL documentation sometimes mentions that compositekeys are just concatenated respective fields (columns).

Actually, it might be that I did apply the REPLACE or IGNORE approach to a composite-keyedtable (and it was InnoDB at that time, now for that project I'm using MyISAM to save space). But I'm

unsure - didn't check the code since it was written (now almost a year ago).

12. cakirhal Says:October 29th, 2008 at 11:24

thanks. it is very useful. Sometimes we want to send pop-up messagebox when we changed or


10/15

ignord the same record. Your solutions are good but I want to know how to inform user that we

changed or ignored the record. For example: "Customer couldn't be added. Because the customer you

entered is already exists." So how can I determine whether users attempt is executed or ignored?

13. Bogdan Says:October 29th, 2008 at 13:01

Cakirhal,

first of all, you will need to consult MySQL documentation for the exact queries you are using - the

"returned rows"/"affected rows" count might be helpful.

Also, before executing the actual modification query, you can execute selection query (i.e.

"SELECT ... FROM") in your program, to know for sure if the customer exists. After that, it is a trivial

task to notify the user of any problems.14. Todd Says:

January 29th, 2009 at 16:41

Thank you for the concise explanation.

15. Jacinto Says:

June 24th, 2009 at 19:33

thank you for your help, you are the best


11/15


12/15


13/15


14/15


15/15

Documents

Of the Latest MySQL, Syntax Presented in the Title is Not Possible