在SQL中使用DECODE语句

Question

我一直在尝试学习SQL，我正在学习DECODE语句：

这是我试图使用的查询：

SELECT DECODE(FIRST_NAME,'Steven','Name is Steven','Neena','Name is Neena','Some other name') AS "NAME" FROM hr.employees;

此查询工作成功，但当我尝试查询时：

SELECT DECODE(FIRST_NAME,'Steven','Name is Steven','Neena','Name is Neena','Some other name') AS "NAME" WHERE FIRST_NAME='Steven' FROM hr.employees;

此查询的输出为：

ORA-00923: FROM keyword not found where expected

有人能解释我怎么了吗？

Answer 1

Where子句需要放在From子句之后。

SELECT DECODE(FIRST_NAME,'Steven','Name is Steven','Neena','Name is Neena','Some other name') AS "NAME"  
FROM hr.employees
WHERE FIRST_NAME='Steven';