在sql中，什么时候用select和select count和select count as 在sql中，什么时候用select和select count...
\u5728sql\u4e2d\uff0c\u4ec0\u4e48\u65f6\u5019\u7528select\u548cselect count\u548cselect count as\uff1fselect count \u548cselect count as \u662f\u4e00\u6837\u7684\uff0c\u90fd\u662f\u7edf\u8ba1\u7b26\u5408\u6761\u4ef6\u8d44\u6599\u7b14\u6570\u3002select count \u67e5\u8be2\u51fa\u7684\u7ed3\u679c\u6ca1\u6709\u680f\u4f4d\u540d\u3002select count as \u53ef\u4ee5\u5bf9\u67e5\u8be2\u51fa\u7684\u7ed3\u679c\u6307\u5b9a\u680f\u4f4d\u540d
SELECT \u662f\u67e5\u8be2\u8d44\u6599\u8868\u91cc\u9762\u7684\u680f\u4f4d\u80fd\u5bb9\u7b49.
select \u4f5c\u4e3a\u67e5\u8be2\u6ee1\u8db3\u4f60\u67e5\u8be2\u8981\u6c42\u7684\u5177\u4f53\u5b57\u6bb5\u4fe1\u606f\u65f6\u4f7f\u7528
select count \u5219\u662f\u7528\u4e8e\u8fd4\u56de\u6ee1\u8db3\u4f60\u67e5\u8be2\u8981\u6c42\u7684\u6240\u6709\u884c\u7684\u603b\u884c\u6570\u7edf\u8ba1
select count是分组查询，目的是统计数量；
select count as 和select count是一样的，AS后面是给统计数量生成的列给个名字，不要as直接空格给个名字也可以的。
select用来查询数据
count是mysql的内置函数，功能是统计符合where条件的记录数量
count as 是指给选出的结果起个名字
加入要判断一个表中有多少条数据就可以使用
seletc count(id) from table
这样选出来的结果就是 count(id)=条数
如果云用seletc count(id) as a from table
选出来的就是 a=条数
select是sql查询语句，涉及到查询的都要用select
select count，count是统计函数，例如：select count(*) from tab就是统计tab表数据总数
select count as，as是起别名，select count(*) as alldata from tab和select count(*) from tab作用是一样的，只是给count(*)起别名为alldata
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