条件查询结果

Question

这里有一个问题的简化。 我有下表：

trigger

我想编写一个查询let data = { "0": { "trigger": 17 }, "1": { "trigger": 3 }, "2": { "trigger": 40 }, "3": { "trigger": 4 }, "4": { "trigger": 19 }, "5": { "trigger": 70 }, "6": { "trigger": 80 }, "7": { "trigger": 0 }, "8": { "trigger": 0 }, "9": { "trigger": 5 }, "10": { "trigger": 4 } } let arrVal = []; for (var keys in data) { arrVal.push(data[keys].trigger) }; console.log(arrVal)的查询，如果是，则在 ad hoc 创建的列中返回Student_table +-----------+--------------------+---------------------+ | Student | Graduation_date | First_working_date | +-----------+--------------------+---------------------+ | John | 12/10/2013 | 15/03/2015 | | Alan | 22/05/2014 | 12/04/2014 | | Lucy | 14/03/2014 | 14/03/2014 | +-----------+--------------------+---------------------+ 值。

这样的事情：

Graduation_date is <= First_working_date

有这样的结果

True

我在Oracle DB（12g）上使用Sql。

Answer 1

在SQL中使用以下CASE-WHEN-ELSE expression：

SELECT student, 
   ( CASE WHEN Graduation_date <= First_working_date THEN 'TRUE'
          ELSE 'FALSE'
          END ) AS Early_Worker
   FROM student_table;

STUDENT EARLY_WORKER
------- ------------
 John   TRUE
 Alan   FALSE
 Lucy   TRUE

SQL Fiddle Demo

Answer 2

这是查询：

SELECT Student,(CASE WHEN Graduation_date <= First_working_date 
THEN
 'TRUE' ELSE 'FALSE' END) AS Early_Worker
from student_table

Answer 3

您可以尝试使用此方法：

SELECT Student,
CASE WHEN(Graduation_date <= First_working_date) THEN 'True'
ELSE 'False' END AS Early_worker
FROM student_table