MySql 插入数据前判断数据是否存在

语法格式：

INSERT INTO table(field1, field2, fieldn) SELECT 'field1', 
'field2', 'fieldn' FROM DUAL WHERE NOT EXISTS(SELECT field FROM 
table WHERE field = ?)

例子：

INSERT INTO t_base_employee(EmpName,EmpNum,EmpPwd,EmpBase,IsAdmin) 
SELECT  '张三','100001','100001','基地名称',0
FROM DUAL 
WHERE NOT EXISTS(SELECT * FROM  t_base_employee WHERE EmpNum = '100001');