What happens when I convert a TEXT column to a MEDIUMTEXT column?

Question

Assuming I have a table with a TEXT column, and there is data in it, what happens when I change that column from TEXT to MEDIUMTEXT, and is there something that I should be aware of or avoid?

Could there be any corruption or loss of data?

Note:

I'm converting from a smaller to a larger type. There should not be any truncation.
I'm aware of the lengths of the different types.
What I want to know is what happens during conversion and how does that affect data?

Till · Answer 1 · 2016-04-06T13:12:16.433

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You will have more characters allowed by row :

      Type | Maximum length
-----------+-------------------------------------
  TINYTEXT |           255 (2 8−1) bytes
      TEXT |        65,535 (216−1) bytes = 64 KiB
MEDIUMTEXT |    16,777,215 (224−1) bytes = 16 MiB
  LONGTEXT | 4,294,967,295 (232−1) bytes =  4 GiB

edited Apr 06 '16 at 13:12

answered Apr 06 '16 at 11:05

Till

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Since when is 16MiB less than 64KiB? – kaqqao Apr 06 '16 at 11:08
@Till I'm converting from a smaller to a larger type. There should not be any truncation. – Apr 06 '16 at 11:15
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Sorry for the misunderstanding. Indeed there will be no changes in your data. – Till Apr 06 '16 at 13:11

score 1 · Answer 2 · edited May 23 '17 at 12:09

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See the answer here for maximum sizes for different column types. Since you're changing from smaller to bigger type, you don't need to worry about truncation. It's a safe operation. Also, you very probably have no index on that column, so not much to worry about there either.

edited May 23 '17 at 12:09

Community

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answered Apr 06 '16 at 11:07

kaqqao

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What happens when I convert a TEXT column to a MEDIUMTEXT column?

2 Answers2