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Re: text vs varchar
Posted by: hua kai ()
Date: May 02, 2016 08:02PM

Øystein Grøvlen, Rick

Thank you very much for your answer

So here is my conclusion for (innodb):

1. At storage level, they are same, Short values will be stored on same page as rest of row, long values will be stored on separate pages.

2. When fetching data from INNODB(no temporary table considered), the server will allocate memory for VARCHAR even if they are not read in select sql, but TEXT will not. So it's better to use TEXT instead of VARCHAR if defined in a same table, or if you want to use VARCHAR which is seldom used, it's better to define in a separated table

3. When temporary table case, VARCHAR(n) when n < 512, could use tmp table in memory. n > 512 or text, it can not use memory, will create tmp table on disk

Am I correct?

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Subject Views Written By Posted
text vs varchar 753 hua kai 04/28/2016 08:36AM
Re: text vs varchar 377 Øystein Grøvlen 04/29/2016 12:41AM
Re: text vs varchar 390 Rick James 04/30/2016 11:51PM
Re: text vs varchar 419 Øystein Grøvlen 05/02/2016 04:37AM
Re: text vs varchar 358 hua kai 05/02/2016 09:14PM
Re: text vs varchar 367 Øystein Grøvlen 05/03/2016 02:19AM
Re: text vs varchar 557 hua kai 05/03/2016 04:12AM
Re: text vs varchar 340 hua kai 05/02/2016 08:02PM
Re: text vs varchar 462 Øystein Grøvlen 05/03/2016 02:25AM

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