Examples to explain query optimization technology of MySQL database (1)_PHP tutorial

Although there are indexes on customer_num and order_num, in the above statement, the optimizer still uses the sequential access path to scan the entire table. Because this statement retrieves a set of separated rows, it should be changed to the following statement:

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http://www.bkjia.com/PHPjc/631004.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/631004.htmlTechArticleAlthough there are indexes on customer_num and order_num, the optimizer still uses the sequential access path in the above statement Scan the entire table. Because this statement retrieves separate rows...