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i have a table: user_friends with: userid int, friendid int... now i do select * from user_friends where userid=2 or friendid=2, i have primary key(userid,friendid), index(friendid), but that query uses no index, why??
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i have a table: user_friends with: userid int, friendid int... now i do select * from user_friends where userid=2 or friendid=2, i have primary key(userid,friendid), index(friendid), but that query uses no index, why??

index problem

SQL (Structured Query Language) is designed to be used in conjunction with relational database products as of a means of working with sets of data. SQL consists of data definition, data manipulation, and procedural elements. Its scope includes data insert, query, update and delete, schema creation and modification, and data access control.