Mysql explain extended

While many people are familiar with the MySQL EXPLAIN comman fewer people are familiar with “ explain extended” which was added in MySQL 4. You might not know this, but MySQL can dramatically change your query before it actually executes it. EXPLAIN EXTENDED …can show you what the MySQL optimizer does to your query. The filtered column indicates an estimated percentage of table rows that will be filtered by the table condition. You can also add the keyword EXTENDED after EXPLAIN in your query and MySQL will show you additional information about the way it executes the query. To see the information, follow your EXPLAIN.

That is, MySQL explains how it would process the statement, including information about how tables are joined and in which order. EXPLAIN returns a row of information for each table used in the SELECT statement. The EXPLAIN statement provides information about how MySQL executes statements.

It lists the tables in the output in the order that MySQL would read them while processing the statement. Looking For Mysql Database? We Have Almost Everything On eBay. Check Out Mysql Database On eBay.

Cost-effective and easy to use SQL Server performance monitoring tool. Its use in a warning, and it will be removed from EXPLAIN syntax in a future MySQL release. One nice feature added for EXPLAIN statement in MySQL 4. It should be used together with SHOW WARNINGS to get information about how query looks after transformation as well as what other notes optimizer may wish. There are less than 10entries in this table.

EXTENDED keyword which provides you with some helpful additional information on query optimization. WHERE used to check if the item is actually published. One method I’ve seen used is to map the time windows to spatial geometries. Doing so allows you to easily check for intersection in an efficient manner. In the query above, START WITH defines the root of the tree, and CONNECT BY defines join condition between parent and child rows.

Parent columns are defined by adding PRIOR keyword to them. In MySQL there is no such construct, but it can be emulated. We may try construct a sorting function somehow,.

Find and fix SQL Server problems quickly and easily with IDERA’s SQL Diagnostic Manager. EXPLAIN PARTITIONS is useful for examining queries involving partitioned tables. However there is no substitute for EXPLAIN ANALYZE. If this blows up in unforeseen ways in the future, this is the CS to revert. How do analyse and use EXPLAIN for my stored procedure calls ? I need to optimize the query time, however seems like there is no where i can do a EXPLAIN call proc_name() ? This crash was fixed in MySQL 5. Understanding MySQL key_len in Explain Statement.

According to MySQL website, the key_len column indicates the length of the key that MySQL decided to use. The length is NULL if the key column says NULL. Note that the value of key_len enables you to determine how many parts of a multiple-part key MySQL actually uses.