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Editor to share with you how to count the number of records after MySQL grouping. I hope you will gain a lot after reading this article. Let's discuss it together.

After MySQL grouping, the method of counting the number of records: 1, count the number of records, the code is [SELECT num,count (*) AS counts from test_a GROUP BY num]; 2, the statistics of the number of num after deduplicating.

After grouping MySQL, the method of counting the number of records:

After grouping, count the number of records:

SELECT num,count (*) AS counts from test_a GROUP BY num

The query results are as follows:

Statistics on the number of num after weight removal:

SELECT count (t.counts) FROM (SELECT num,count (*) AS counts from test_a GROUP BY num) AS t; SELECT count (DISTINCT num) AS count FROM test_a

They both have the same result, 5; only one is a subquery (nested), and the other is the built-in function distinct ()

Database structure

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