CODEWITHSUNDEEP
mysql
Agent96
Agent96

Reputation: 475

MySql max key too long with a key less then 767

Strange question, I have been creating database tables on my local mysql for years now, and I have just got an error message:

Specified key was too long; max key length is 767 bytes

The column at fault is the following:

`referenceperiod` VARCHAR(300) NULL

notice the length of 300, which, the last time I checked is less then 767. I have an index on this column which if I remove allows the table to be built:

INDEX `idx_referenceperiod` (referenceperiod),

The strange thing is, this is not the first time I have built this exact table - so why is it suddenly failing now...

Upvotes: 1

Views: 44

Answers (1)

GolezTrol
GolezTrol

Reputation: 116180

If you have a UTF8 collation, MySQL reserves 3 bytes for each character, in which case the key becomes 900 bytes in total.

900 is more than 767, last time I checked. ;)

Upvotes: 2

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