SUM函数的语法是：
SELECT SUM(expression )
FROM tables
WHERE predicates;
表达式可以是一个数值字段或公式。
SELECT column1+ column1 + column1 …… + column1 AS Total FROM table
SUM函数的语法是：SELECT SUM(expression ) FROM tables WHERE predicates;表达式可以是一个数值字段或公式。SELECT 列1+列2+列3……+列N AS Total FROM 表或者select SUM(group_type+group_num_d
count() as ‘下发数’,
SUM(b.sflxs is not null) as ‘核查数’,
SUM(b.sflxs is not null)/count() as ‘完成率’,
SUM(b.sflxs=1 and b.sfchbl=1 and b.szdq=1) as ‘查实数’,
SUM(b.sflxs=1 and b.sfchbl=1 and b.
例如，要将表中id为1的行的name列修改为"张三"，age列修改为20，可以使用以下语句：
UPDATE student SET name='张三', age=20 WHERE id=1;
注意，WHERE子句是必须的，否则会将所有行的数据都修改。
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