COUNT() 函数返回匹配指定条件的行数
SQL COUNT(column_name) 语法
COUNT(column_name) 函数返回指定列的值的数目 (NULL 不计入):
SELECT COUNT(column_name) FROM table_name;
示例: select count(brand_name) as num from sec_financial_product_shop_relate where shop_code=000055
SQL COUNT(*) 语法
COUNT(*) 函数返回表中的记录数:
SELECT COUNT(*) FROM table_name;
示例: select count(*) as num from sec_financial_product_shop_relate where shop_code=000055
SQL COUNT(DISTINCT column_name) 语法
COUNT(DISTINCT column_name) 函数返回指定列的不同值的数目:
SELECT COUNT(DISTINCT column_name) FROM table_name;
示例: select count(distinct brand_name) as num from sec_financial_product_shop_relate where shop_code=000055
注释: COUNT(DISTINCT) 适用于 ORACLE 和 Microsoft SQL Server, 但是无法用于 Microsoft Access.
SUM() 函数
SUM() 函数返回数值列的总数.
SQL SUM() 语法
SELECT SUM(column_name) FROM table_name;
示例: SELECT SUM(score) AS nums FROM score_info where subject='语文';
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