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What size varchar should I use?
Values in VARCHAR columns are variable-length strings. The length can be specified as a value from 0 to 65,535. The effective maximum length of a VARCHAR is subject to the maximum row size (65,535 bytes, which is shared among all columns) and the character set used.
Which is faster CHAR or varchar?
VARCHAR is used to store variable length character strings up to 4000 characters. But, remember CHAR is faster than VARCHAR – some times up to 50% faster.
Does varchar length matter?
Yes, is matter when you indexing multiple columns. Prefixes can be up to 1000 bytes long (767 bytes for InnoDB tables). Note that prefix limits are measured in bytes, whereas the prefix length in CREATE TABLE statements is interpreted as number of characters.
Is varchar fixed size?
The short answer is: VARCHAR is variable length, while CHAR is fixed length. CHAR is a fixed length string data type, so any remaining space in the field is padded with blanks. CHAR takes up 1 byte per character. So, a CHAR(100) field (or variable) takes up 100 bytes on disk, regardless of the string it holds.
What does varchar 255 mean?
The length can be specified as a value from 0 to 65,535. The effective maximum length of a VARCHAR is subject to the maximum row size (65,535 bytes, which is shared among all columns) and the character set used. VARCHAR(255) stores 255 characters, which may be more than 255 bytes.
What happens when there are too many varchars in a database?
Too many long VARCHARs can lead to failure of CREATE TABLE. A complex SELECT will use a temp table to, for example, do the sorting for an ORDER BY. A MEMORY table is used in some situations. In other situations, MyISAM will be used. When using MEMORY, VARCHARs are turned into CHARs (for the temp table).
Is it possible to increase the size of A varchar column?
For SQL Server I could not find a clear statement on this but the execution time to increase the size of a varchar column (again the 1.2 million rows table from above) indicates that no rewrite takes place. Seems I was (at least partially) wrong about SQL Server.
Which is better A varchar or a length in MySQL?
MySQL – varchar length and performance. So the general piece of advice is to use the smallest type possible, because it can potentially create performance or management problems otherwise. A VARCHAR(100) is better than VARCHAR(255) (although a VARCHAR(20) would be better), even if you do not know the exact length.
Is there a limit on index size in MySQL?
You could overflow a limit on index size. Complex SELECTs may need a temp table, and may use MEMORY for it. In this case, VARCHAR (255) becomes CHAR (255) for the temp table. And, if using utf8, that is 755 bytes for every row! (8.0 fixes this design flaw?)