具体数据查询

Question

Link 上一个线程 - 已链接

总结

Based on the link above, I have continued to code more specfic result that I want, which i have met some problem during the code which is using "WHERE" statement for showing specfic data after using subsitution variable(&)

基于 Mr.Barboros 提供的工作代码，我想添加一些查询以仅显示某些位置，例如，

我有查询 2016 ，应该只显示 2 个结果

FACILITYNAME COUNT_TIMES    MONTHS
Science Lab     1             4
Science Lab     1             5

But it always show extra Location which is Biology even in 2016 there is no Biology inserted to the DB. - If i added more location with "OR" , it will still continue show the result , below is the code for my query.

SELECT f.FACILITYNAME,COUNT(*) AS count_times, EXTRACT (MONTH FROM b.Timebooked ) AS MONTHS
FROM BookingTable b
JOIN FacilityTable f ON b.FACILITYNO = f.FACILITYNO
WHERE TO_CHAR(b.Timebooked , 'YYYY') = 2018
AND f.FACILITYNAME = 'Toilet' OR f.FACILITYNAME = 'Science Lab' OR  f.FACILITYNAME = 'Biology Lab'
GROUP BY (EXTRACT (MONTH FROM b.Timebooked )),f.FACILITYNAME
ORDER BY (EXTRACT (MONTH FROM b.Timebooked ));

http://sqlfiddle.com/#!4/13a6a/9

The result that I want is, when i entered any year , only show Toilet,Science Lab Biology Lab

Answer 1

需要在 'OR' 组条件周围添加“()”。如果没有括号，AND 将优先于 OR。参考SQL Logic Operator Precedence.

试试这个：

SELECT f.FACILITYNAME,COUNT(*) AS count_times, EXTRACT (MONTH FROM b.Timebooked ) AS MONTHS
FROM BookingTable b
JOIN FacilityTable f ON b.FACILITYNO = f.FACILITYNO
WHERE TO_CHAR(b.Timebooked , 'YYYY') = 2018
AND (f.FACILITYNAME = 'Toilet' OR f.FACILITYNAME = 'Science Lab' OR  f.FACILITYNAME = 'Biology Lab')
GROUP BY (EXTRACT (MONTH FROM b.Timebooked )),f.FACILITYNAME
ORDER BY (EXTRACT (MONTH FROM b.Timebooked ));

没有括号，您的查询实际上是这样做的（这是不正确的）：

SELECT f.FACILITYNAME,COUNT(*) AS count_times, EXTRACT (MONTH FROM b.Timebooked ) AS MONTHS
FROM BookingTable b
JOIN FacilityTable f ON b.FACILITYNO = f.FACILITYNO
WHERE ( TO_CHAR(b.Timebooked , 'YYYY') = 2018
AND  f.FACILITYNAME = 'Toilet') OR f.FACILITYNAME = 'Science Lab' OR  f.FACILITYNAME = 'Biology Lab' 
GROUP BY (EXTRACT (MONTH FROM b.Timebooked )),f.FACILITYNAME
ORDER BY (EXTRACT (MONTH FROM b.Timebooked ));

具体数据查询

Specific Data Query

sql

oracle

operators

oracle11g