日期:2014-05-16 浏览次数:20509 次
查询插入:insert into table_A(col1,col2) select col1,col2 from tab_B where condition;
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补齐函数:lpad(col1,length,'a'),左边补齐函数,用于处理数据,将col1列的数据,格式化成固定length长度的字符,不足长度时用'a'补充,rpad是右边补齐函数
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空值转换:nvl(col1,'a'),将col1列的NULL值或者空值转换成'a'
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CASE查询:case?? SELECT cust_last_name, CASE credit_limit WHEN 100 THEN 'Low'?? WHEN 5000 THEN High'?? ELSE 'Medium' END?? FROM customers;
SELECT department_id FROM departments d WHERE EXISTS (SELECT * FROM employees e WHERE d.department_id = e.department_id);