oracle常用到的函数

1.将字符串转成大写：nls_upper()
NLS_UPPER(T.TRADE_MARKET) IN ('SHANGHAI STOCK EXCHA', 'SHENZHEN STOCK EXCHA')

2.nvl函数：从两个表达式返回一个非 null 值
select nvl(a.name,'空得') as name from student a join school b on a.ID=b.ID
也可以用在where条件中：
select * from amc_biz_rec t where nvl(t.stock_settled_date,t.cash_settled_date) <=?;

但是：注意where中使用nvl的话，会忽略掉一种情况。

t.stock_settled_date不为空，且不满足条件的话，则不会判断下一个。

即：nvl(t.stock_settled_date,t.cash_settled_date) <=? 不等价于

t.stock_settled_date <=? or t.cash_settled_date<=?

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3.lengthb函数：如果汉字的话，长度会返回2