CODEWITHSUNDEEP
sqlmysqlalter-tableerror-log
Blackarch
Blackarch

Reputation: 1

Does MySql ALTER TABLE command affects rows?

I'm using query

ALTER TABLE `DEPLOYMENT` CHANGE COLUMN `ID_` `ID_` VARCHAR(100) NOT NULL 
-> 72 row(s) affected Records: 72 Duplicates: 0 Warnings: 0  0.281 sec

But 2nd time while executing same query

ALTER TABLE `DEPLOYMENT` CHANGE COLUMN `ID_` `ID_` VARCHAR(200) NOT NULL  
0 row(s) affected Records: 0 Duplicates: 0 Warnings: 0  0.265 sec

Does it really affects the data?

Upvotes: -1

Views: 217

Answers (1)

Barmar
Barmar

Reputation: 782166

Increasing the length of a VARCHAR column doesn't need to modify any rows, unless the length changes from 1-255 to 256-65535. In that case it has to add a byte to the length field, which will affect every row.

Upvotes: 1

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