EXPLAIN Output Format •When  EXPLAIN  is used with  FOR CONNECTION  connection_id  rather than an explainable statement, it displays the execution plan for the statement executing in the named connection. See Section 8.8.4, “Obtaining Execution Plan Information for a Named Connection” . •For  SELECT  statements,  EXPLAIN  produces additional execution plan information that can be displayed using  SHOW WARNINGS . See Section 8.8.3, “Extended EXPLAIN Output Format” . • EXPLAIN  is useful for examining queries involving partitioned tables. See Section 24.3.5, “Obtaining Information About Partitions” . •The  FORMAT  option can be used to select the output format.  TRADITIONAL  presents the output in tabular format. This is the default if no  FORMAT  option is present.  JSON  format displays the information in JSON format.  With the help of  EXPLAIN , you can see where you should add indexes to tables so that the statement executes faster by using indexes to find rows. You can also use  EXPLAIN  to check whether the optimizer joins the tables in an optimal order. To give a hint to the optimizer to use a join order corresponding to the order in which the tables are named in a  SELECT  statement, begin the statement with  SELECT STRAIGHT_JOIN  rather than just  SELECT . (See Section 13.2.10, “SELECT Statement” .) However, STRAIGHT_JOIN  may prevent indexes from being used because it disables semijoin transformations. See Section 8.2.2.1, “Optimizing IN and EXISTS Subquery Predicates with Semijoin Transformations” . The optimizer trace may sometimes provide information complementary to that of  EXPLAIN . However, the optimizer trace format and content are subject to change between versions. For details, see MySQL Internals: Tracing the Optimizer. If you have a problem with indexes not being used when you believe that they should be, run  ANALYZE TABLE  to update table statistics, such as cardinality of keys, that can affect the choices the optimizer makes. See Section 13.7.3.1, “ANALYZE TABLE Statement” . Note 8.8.2 EXPLAIN Output Format EXPLAIN  can also be used to obtain information about the columns in a table.  EXPLAIN  tbl_name  is synonymous with  DESCRIBE  tbl_name  and SHOW COLUMNS FROM  tbl_name . For more information, see Section 13.8.1, “DESCRIBE Statement” , and Section 13.7.7.5, “SHOW COLUMNS Statement” . The  EXPLAIN  statement provides information about how MySQL executes statements.  EXPLAIN  works with  SELECT ,  DELETE ,  INSERT ,  REPLACE , and  UPDATE  statements. EXPLAIN  returns a row of information for each table used in the  SELECT  statement. It lists the tables in the output in the order that MySQL would read them while processing the statement. This means that MySQL reads a row from the first table, then finds a matching row in the second table, and then in the third table, and so on. When all tables are processed, MySQL outputs the selected columns and backtracks through the table list until a table is found for which there are more matching rows. The next row is read from this table and the process continues with the next table. MySQL Workbench has a Visual Explain capability that provides a visual representation of  EXPLAIN  output. See Tutorial: Using Explain to Improve Query Performance. Note •EXPLAIN Output Columns •EXPLAIN Join Types 1762