mysql varchar length performance

This article describes in detail the performance and space occupied by varchar (n) and nvarchar (n) in SQL. For more information, see. This article describes in detail the performance and space occupied by varchar (n) and nvarchar (n) in SQL. For more information, see. How to explain n in

-sensitive, and the text value is case insensitive. In other words, a text is a case-insensitive blob.4. Summarize the difference between Char,varchar and textThe length of the difference, Char range is 0~255,varchar the longest is 64k, but note here 64k is the length of the entire row, to consider the other column, an

length of the difference, Char range is 0~255,varchar the longest is 64k, but note here 64k is the length of the entire row, to consider the other column, and if there is not NULL when it will occupy a bit, for different character sets, effective length is not the same, such as UTF8, up to 21845, but also to remove th

business logic is only for the char type design, so the database software also retains the char type. 2, the char type is fixed long, some database can not store the field length information in each record, this can save partial space, also can make some memory alignment to improve performance, but personally think this brings the performance improvement very s

does not, text can only store plain text files. The 4 text types Tinytext, text, Mediumtext, and Longtext correspond to 4 blob types and have the same maximum length and storage requirements. The only difference between blob and text types is that the sorting and comparison of BLOB values is case-sensitive, and the text value is case insensitive. In other words, a text is a case-insensitive blob.4. Summarize Char,

example, CHAR (30) can hold up to 30 characters. (Before MySQL 4.1, the length is interpreted as number of bytes .) Let's take a look at similar descriptions of other versions: The code is as follows: The CHAR and VARCHAR types are declared with a length that indicates the maximum number of characters you want to st

In a database, character-type data is the most, and can account for more than 80% of the entire database. It is very important to improve the performance of database to deal with character data correctly. In character data, the most used is char and varchar two kinds. The front is fixed length, and the following is a variable

In a database, the majority type of data accounts for more than 80% of the total database. Therefore, correct processing of structured data can greatly improve database performance. In character data, Char and Varchar are the most common types. The front is a fixed length, while the back is a variable length. Now we ne

maximum-length character in the character set BINARY (M) m bytes, 0 m VARCHAR (m), VARBINARY (m) l + 1 bytes If column values require 0–255 bytes, l + 2 bytes If values may require more than 255 bytes Tinyblob, tinytext l + 1 bytes, where L 8 BLOB, TEXT l + 2 bytes, where L Mediumblob, mediumtext l + 3 b

varchar type on the update link is much larger than the char type, so char is suitable for applications where fields are frequently updated . (2) varchar saves disk space (3) When large data volume extraction, varchar disk IO consumption is lower, which means that the performance of

Recently a few students asked me varchar and text have what do not, this problem, previously said really did not much collation, before the text in the design is as far as possible to the other table, to keep the main table as small as possible, so that the InnoDB BP cache more data. Today, the system of opportunity to clean up, mainly from the storage, the maximum value, the default value of several aspects of comparison. BTW: from the ISO sql:2003

Label:varchar and char are two of the most important string types. Unfortunately, it is difficult to explain precisely how these values are stored on disk and in memory because of the specific implementation of this storage engine. The following description assumes that the storage engine used is InnoDB or MyISAM. If you are not using either of these storage engines, refer to the documentation for the storage engine you are using.Let's look at how varchar