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查询不为空的所有记录
SELECT id,firstname,lastname,mail FROM testdb.users WHERE mail!='';
或者
SELECT id,firstname,last本文来源gao($daima.com搞@代@#码(网name,mail FROM testdb.users WHERE LENGTH(mail)>0;
mysql查询一个表的记录的总数
SELECT count(*) FROM table_name;
或者
SELECT count(*) as num FROM table_name;
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