Ask a question about php+mysql.

Ask a question about php+mysql.
To query data in a table, the condition is UID in (all-in-one). So satisfying uid=1 or 2 or 3 of the query.
How do I get one condition for each meeting?
For example, the UID is a few of the three, through the SQL query, only the first UID is 1, the UID is the first of 2, the UID is the first of 3.
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First of all your data must have an ID, a UID

The query uid is a few: (assuming that the table is named ' User ', there are only two fields in the table, ID and UID, respectively)

Select Id,count (UID) from the user group by UID has uid=1 or uid=2 or uid = 3;

The first of the query UID is 1:

SELECT * from user where uid=1 limit 1;

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You can take one of the resulting sets of queries in groups
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Where (select COUNT (*) from tbl_name where Uid=a.uid and ID
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Only one rule is taken for each condition:
SELECT * from the TT where UID in (n/a) group by UID;
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Select  a.*  from  table A where  1> (select COUNT (1) from table B where a.id = b.ID and a.id > b.ID) A nd a.uid in (All-in-all)
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Select top 1 * from table GROUP BY  
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Group by can achieve
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