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Examples to explain query optimization technology of MySQL database (1)_PHP tutorial
- WBOYOriginal
- 2016-07-13 17:03:08856browse
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:
(T114)
Statement：
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