GROUP BY 語句根據(jù)一個(gè)或多個(gè)列對(duì)結(jié)果集進(jìn)行分組痘绎。
在分組的列上我們可以使用 COUNT, SUM, AVG,等函數(shù)
使用 WITH ROLLUP
WITH ROLLUP 可以實(shí)現(xiàn)在分組統(tǒng)計(jì)數(shù)據(jù)基礎(chǔ)上再進(jìn)行相同的統(tǒng)計(jì)（SUM,AVG,COUNT…）含长。
SELECT name, SUM(singin) as singin_count FROM employee_tbl GROUP BY name WITH ROLLUP;
