MySQL分組后，如何統(tǒng)計(jì)記錄條數(shù)

MySQL分組后，統(tǒng)計(jì)記錄條數(shù)的方法：1、統(tǒng)計(jì)記錄條數(shù)，代碼為【SELECT num,count(*) AS counts from test_a GROUP BY num】；2、對(duì)num去重后的數(shù)量的統(tǒng)計(jì)。

MySQL分組后，統(tǒng)計(jì)記錄條數(shù)的方法：

分組后，統(tǒng)計(jì)記錄條數(shù)：

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

查詢結(jié)果如下：

對(duì)num去重后的數(shù)量的統(tǒng)計(jì)：

　　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;

　　它倆結(jié)果一樣，都是5；只是一個(gè)是子查詢（嵌套），一個(gè)是內(nèi)置函數(shù) distinct（）；

數(shù)據(jù)庫(kù)結(jié)構(gòu)