To rename a table in MySQL you just need to run a command named RENAME TABLE, the syntax is very easy to use. RENAME TABLE table1 TO table2; The RENAME TABLE command will rename the table atomically, which means your table will be locked during the command. You can also rename more than one … Read more
Very often we need to extract last 30 days, 7 days data from mysql DB. Here we will show easy way to get the data of given interval. SELECT DATE_FORMAT(create_date, ‘%m/%d/%Y’) FROM mytable WHERE create_date BETWEEN CURDATE() – INTERVAL 30 DAY AND CURDATE() Also note that CURDATE() returns only the DATE portion of the date, so … Read more
The myisamchk utility gets information about your database tables or checks, repairs, or optimizes them. myisamchk works with MyISAM tables (tables that have .MYD and .MYI files for storing data and indexes). The use of myisamchk with partitioned tables is not supported. How to run this Utility – myisamchk myisamchk [options] tbl_name The options specify … Read more
In this post we will see how can we optimize where clause. Where clause restrict the result set to a range. Basically this is used to access the range of a table/view. The range access method uses a single index to retrieve a subset of table rows that are contained within one or several index … Read more
MySQL SUBSTRING() returns a specified number of characters from a particular position of a given string. Syntax: SUBSTRING(str, pos, len) or SUBSTRING(str FROM pos FOR len) Arguments Name Description str A string. pos Starting position. len … Read more
Syntax: IF(expr,if_true_expr,if_false_expr) MySQL IF function is control flow functions that returns a value based on a condition. The IF function is sometimes referred to as IF ELSE or IF THEN ELSE function. If the expr evaluates to TRUE i.e., expr is not NULL and expr is not 0, the IF function returns the if_true_expr , … Read more
The busiest file in the InnoDB infrastructure is /var/lib/mysql/ibdata1 This file normally houses many classes of information (when innodb_file_per_table is 0) Table Data Table Indexes MVCC (Multiversioning Concurrency Control) Data Rollbacks Segments Undo Tablespace Table Metadata Many people create multiple ibdata files hoping for better diskspace management and performance. It does not help. Unfortunately, OPTIMIZE TABLE against … Read more