![]() ![]() I often come across columns that are varchar (255), so presumably this is a convention of sorts. That means compressing the 32 characters (36 or more with separators) to the 16-bit format or back to the human-readable format. If I’m wrong about what I took away from reading today, please let me know in the comments. 11 This question already has answers here : MySQL - varchar length and performance (2 answers) Closed 4 years ago. These function will be used to convert from the human-readable format (char/varchar) to the compact format (binary) and back. While doing this, I discovered that about half our UUIDs are v1, and the other half are v4. The length can be any value from 0 to 255. The length of a CHAR column is fixed to the length that you declare when you create the table. For example, CHAR (30) can hold up to 30 characters. I was recently asked to add a column to this table of VARCHAR(32) that stores the non-dashed UUID hex. The CHAR and VARCHAR types are declared with a length that indicates the maximum number of characters you want to store. The varchar columns in the table are of variable length string that can hold either numeric or character or both. They are stored in the standard VARBINARY(16). Varchar in MySQL is a data type used for storing text whose length can have a maximum of 65535 characters. Storing UUIDs in a non-character column could make sense, but since UUID() returns characters anyway, it’s going against the grain.Ĭonclusion: Use the CHAR(36) type in MySQL. I have a MySQL InnoDB table with tens of millions of rows.varchar takes extra memory to store a prefix, which I presume to describe the length which char would not need.It’s more likely to make a difference if the column is indexed ( source).( This post claimed a 20% speed improvement by switching to ROW_FORMAT=fixed, which seems related but maybe not the same.) ![]()
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