mysql substring index

062 Creating an indexIndexing is especially important for queries that are the primary application. A lot of times the performance problem is simply because we forgot to add an index, or we didn't add a more efficient index. If you do not index,

The commonly used string truncation functions in mysql include substring and SUBSTRING_INDEX. substring is the string whose pos starts to be len. This is a bit like the php string truncation function, let's take a look. Usage: SUBSTRING (str, pos,

Usage: SUBSTRING (Str,pos,len)SUBSTRING (str from POS for Len)SUBSTRING (Str,pos)SUBSTRING (str from POS) Alias Substr Intercept string str String that starts at the beginning of the POS length of Len, if you do not set the Len parameter to get

Generally, the entire string is used as the operation object, for example: search for a substring in a substring, obtain a substring, insert a substring at a certain position in the substring, and delete a substring. Generally, the entire string is

Turn from "http://www.cnblogs.com/mywebname/articles/555696.html"First, the concept of the indexAn index is a way to speed up the retrieval of data in a table. The index of the database is similar to the index of the book. In books, the index allows

Generally, the entire string is used as the operation object, for example: search for a substring in a substring, obtain a substring, insert a substring at a certain position in the substring, and delete a substring. The required and sufficient

The index of MySQL is the index introduced by the database index application database. The most frequently performed operation on a database is data query. In general, the database needs to search the entire table for data during the query operation.

String function string comparison function if the result length is greater than the maximum value of the max_allowed_packet system variable, the return value of the string value function is NULL. See section 7.5.2 "Adjust server Parameters ". String

String functionsstring comparison functionsIf the length of the result is greater than the maximum value of the Max_allowed_packet system variable, the return value of the string value function is null. See section 7.5.2, "Tuning server parameters."

Generally, the entire string is used as the operation object, for example: search for a substring in a substring, obtain a substring, insert a substring at a certain position in the substring, and delete a substring. The required and sufficient