如果全表是百万级别以上的数据表,那么就这么一个简单的判断,就有可能拖垮数据库。 所以需要先把符合“where条件”的记录,用一个子查询筛选出来,再在筛选结果集里选top30。 因为SQL规则规定,如果子查询里,有order ...,就必须有TOP,所以就用SELECT TOP 100 PERCENT来限定,top 100 percent是为了保证筛选出所有符合...
选择前百分之100
选择前百分之100 SELECT TOP 100 PERCENT 选择前百分之100
SELECT TOP 100 PERCENT是选择前100%的意思
SELECT TOP 100 PERCENT SELECT TOP 100 PERCENT ... order ... 因为作为子查询,如果有order ...,规定必须有TOP,所以就用SELECT TOP 100 PERCENT
--返回符合条件的100%的记录,即所有符合条件的记录 SELECT TOP 100 PERCENT * --返回符合条件的100条记录,即只返回符合条件的100条记录 SELECT TOP 100 * #2 SELECT TOP 100 PERCENT ... order ... 因为作为子查询,如果有order ...,规定必须有TOP,所以就用SELECT TOP 100 PERCENT ...
One of these is the presence of TOP 100 PERCENT or perhaps written as TOP (100) PERCENT in SELECT queries. Almost always, we see this in the definition of views. In SQL Server, a view is basically just a SELECT statement that's been given a name. ...
TOP 100是显示前一百条数据。percent百分比，但不是放在语句里这么用，要实现百分数可以乘100，只显示两位小数，并加上||'%'
100 Percent=100 取对应表中的100%的记录数据；相当于取全部数据
The TOP clause forces the query to only return the first # number or in this case # percent of rows; so specifically here it returns the whole record set as normal (100%). You would need to provide the whole query to know the exact impact. ...