Mysqlin subquery is easy to optimize

When mysqlin subqueries are simply optimized to a large number, do not use in nested subqueries. The performance is poor and it is easy to get stuck .? The simple adjustment method is as follows: selectuid, nick_namefromuc_userswhereuidin (selectfidfromuc_followwhereuid # uid #)? It can be split into: 1. selectfidfromuc_followwher

When a large number of mysql in subqueries are simply optimized, do not use in nested subqueries. The performance is poor and it is easy to get stuck. ? The simple adjustment method is as follows: select uid, nick_name from uc_users where uid in (select fid from uc_follow where uid = # uid #)? It can be split into: 1. select fid from uc_follow wher

Simple Optimization of mysql in subqueries

In a large number of cases, do not use in nested subqueries. The performance is poor and it is easy to get stuck.

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The following is a simple adjustment method:

Select uid, nick_name from uc_users where uid in (select fid from uc_follow where uid = # uid #)

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It can be divided:

1. select fid from uc_follow where uid = # uid #

Pass the result 1 to 2.

2. select uid, nick_name from uc_users where uid in ($ fids $)

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