is the principle of mysql multi-database and multi-table joint query based on Synchronize double writing?
try to find it in books such as mysql performance optimization, but there are no in-depth instructions on database connection pooling
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is currently self-learning mysql,. When querying, sometimes you need to use as aliases, but after adding as aliases to the following two query statements, why is it incorrect? 1, select cat_id,goods_name,shop_price from goods where shop_price in (sele...
as shown in the figure, this association query is different in that it is associated with the same table indicates that table_test requirement: first query the result set of the field whose reply_type is 0, and then use the reply_id of the resul...
< H2 > tables: < H2 > employee employee_orgn: federated primary key (employee_id,orgn_id), index 1, 2:orgn_id employees, index orgn < H2 > sql: < H2 > explain SELECT DISTINCT e.* FROM employee e LEFT JOIN employee_orgn eo ...
what do you usually consider when adding an index? I usually add an index by querying a few fields in the where clause and adding an index to those fields. ...