mysql alter table add index example

ALTER TABLE Syntax ALTER [IGNORE] TABLE tbl_name alter_spec [, Alter_spec ...] Alter_specification:ADD [COLUMN] create_definition [i | After column_name]or ADD [COLUMN] (create_definition, create_definition,...)or ADD INDEX [index_name] (Index_col_

MySQL index details, MySQL index detailsI. Introduction to index basics 1.1 In MySQL, indexes are also called keys. They are a data structure that the storage engine uses to quickly find records. Indexes are critical to good performance. Especially

  From: http://waryist.javaeye.com/blog/104739Waryist blog    Alter [ignore] Table tbl_name alter_spec [, alter_spec...]Alter_specification:Add [column]

First, basic usage 1. Add Column ALTER TABLE Tbl_name add col_name type For example, add a column of weight to the pet table, Mysql>alter table Pet Add weight int; 2. Delete Column ALTER TABLE Tbl_name drop col_

ALTER TABLE allows you to modify the structure of an existing table. For example, you can add or delete columns, create or eliminate indexes, change the type of existing columns, or rename columns or the table itself. You can also change the

The following articles mainly describe the actual operations of modifying the alter TABLE structure in MySQL. If you are interested in the actual operations of modifying the alter TABLE structure in MySQL, you can browse the following articles, the

The alter ADD command is used to increase the table's fields.Alter ADD command format: ALTER TABLE name add field type other;For example, a field passtest is added to table MyClass, the type is int (4), and the default value is 0:Mysql> ALTER TABLE

MySQL 5-1 -- index bitsCN.com 1. MySQL has multiple rows that access tables. The most commonly used is sequential access and index access. Sequential access refers to browsing a table in one row, that is, full table scan. Disadvantage: it is very

MySQL index analysis and optimization indexes are used to quickly search for records with specific values. all MySQL indexes are saved as B-trees. If no index exists, MySQL must scan all the records of the entire table from the first record until

Index functionIn addition to the ordered lookups mentioned above, the database uses a variety of fast location techniques to greatly improve the query efficiency. In particular, when the amount of data is very large and the query involves more than