SQL拥有很多课用于计数和计算的内建函数。
SELECT function(列) FROM 表
SELECT AVG(column_name) FROM table_name
COUNT(column_name)返回指定列的值得数目(NULL不计入) SELECT COUNT(column_name) FROM table_name COUNT(*)返回表中的记录数目 SELECT COUNT(*) FROM table_name COUNT(DISTINCT column_name)返回指定列的不同值的数目 SELECT COUNT(DISTINCT column_name) FROM table_name
SELECT FIRST(column_name) FROM table_name (可以先用ORDER BY对记录排序)
SELECT LAST(column_name) FROM table_name
SELECT MAX/MIN(column_name) FROM table_name
SELECT SUM(column_name) FROM table_name
SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name
SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value
SELECT UCASE/LCASE(column_name) FROM table_name
SELECT MID(column_name, start[,length]) FROM table_name 其中,start规定开始位置(起始值是1) length要返回的字符数。如果省略,则MID()函数返回剩余文本。
SELECT LEN(column_name) FROM table_name
SELECT ROUND(column_name, decimals) FROM table_name
SELECT NOW() FROM table_name
SELECT FORMAT(column_name, formate) FROM table_name
原文:http://www.cnblogs.com/little-YTMM/p/5247489.html