select case when null = null then 1 null <> null then 2 else 3 end result_value from dual;

执行这个 SQL 语句的结果是 3。这是因为在 SQL 中，NULL 值与任何值都不相等，包括 NULL 本身。因此，当执行 `null = null` 时，结果为未知（unknown），而不是 true 或 false，因此会跳过第一个 `when` 子句，执行第二个 `when` 子句。同样，当执行 `null <> null` 时，结果也是未知（unknown），因此会执行 `else` 子句，返回结果值 3。在 SQL 中，判断 NULL 值是否相等或不相等时，应该使用 `is null` 或 `is not null` 来判断，而不是使用 `=` 或 `<>` 运算符。

相关问题

select a.IMSI, a.GJ, a.YYS, count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 then a.IMSI else null end) as MRWZGXQQCS, count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 and b.result<>1 then a.IMSI else null end) as MRWZGXQQCS, case when count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 then a.IMSI else null end)=0 then 0 else count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 and b.result<>1 then a.IMSI else null)/ count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 then a.IMSI else null end) as MRWZGXCGL, sum(c.MRZJCS) as MRZJCS, sum(c.MRZJHJCGCS) as MRZJHJCGCS, sum(d.MRBJCS) as MRBJCS, sum(d.MRBJHJCGCS) as MRBJHJCGCS, case when sum(c.MRZJCS)=0 then 0 else sum(c.MRZJHJCGCS)/sum(c.MRZJCS) end as MRZJWLJTL, case when sum(c.MRZJCS)=0 then 0 else sum(d.MRBJHJCGCS)/sum(d.MRBJCS) end as MRBJWLJTL, count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 then a.IMSI else null end) as MCWZGXQQCS, count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 and b.result<>1 then a.IMSI else null end) as MCWZGXCGCS, case when count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 then a.IMSI else null end)=0 then 0 else count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 and b.result<>1 then a.IMSI else null end)/ count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 then a.IMSI else null end) as MCWZGXCGL from (select * from TAB_A union select * from TAB_B union select * from TAB_C)a left join (select * from spark_odc_dwd.D_ENS_GMAP_MM where p_hour='#{time yyyyMMddHH}') b on a.IMSI=b.IMSI left join TAB_D c on a.IMSI=c.calling_imsi left join TAB_E c on a.IMSI=c.called_imsi group by a.IMSI, a.GJ, a.YYS

这个SQL语句存在两个问题：

1. `count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 and b.result<>1 then a.IMSI else null end)` 这个计数列在前面已经定义过了，而且它的别名与另一个计数列的别名相同，应该更改其中一个别名。

2. `else count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 and b.result<>1 then a.IMSI else null end)/ count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 then a.IMSI else null end)` 这个计算列的语法有误，应该将它单独作为一个计算列，并且在分母为0时设置默认值0。

下面是修改后的SQL语句：

select 
    a.IMSI, 
    a.GJ, 
    a.YYS, 
    count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 then a.IMSI else null end) as MRWZGXQQCS, 
    count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 and b.result<>1 then a.IMSI else null end) as MRWZGXCGCS, 
    case when count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 then a.IMSI else null end)=0 then 0 
         else count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 and b.result<>1 then a.IMSI else null end) / count(case when substr(b.IMSI,1,5)<>46000 and b.operate_code=2 then a.IMSI else null end) 
    end as MRWZGXCGL, 
    sum(c.MRZJCS) as MRZJCS, 
    sum(c.MRZJHJCGCS) as MRZJHJCGCS, 
    sum(d.MRBJCS) as MRBJCS, 
    sum(d.MRBJHJCGCS) as MRBJHJCGCS, 
    case when sum(c.MRZJCS)=0 then 0 
         else sum(c.MRZJHJCGCS)/sum(c.MRZJCS) 
    end as MRZJWLJTL, 
    case when sum(d.MRBJCS)=0 then 0 
         else sum(d.MRBJHJCGCS)/sum(d.MRBJCS) 
    end as MRBJWLJTL, 
    count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 then a.IMSI else null end) as MCWZGXQQCS, 
    count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 and b.result<>1 then a.IMSI else null end) as MCWZGXCGCS, 
    case when count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 then a.IMSI else null end)=0 then 0 
         else count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 and b.result<>1 then a.IMSI else null end) / count(case when substr(b.msc,1,2)<>86 and a.GJ is not null and b.operate_code=2 then a.IMSI else null end) 
    end as MCWZGXCGL 
from  
    (select * from TAB_A union select * from TAB_B union select * from TAB_C) a 
left join  
    (select * from spark_odc_dwd.D_ENS_GMAP_MM where p_hour='#{time yyyyMMddHH}') b on a.IMSI=b.IMSI 
left join  
    TAB_D c on a.IMSI=c.calling_imsi 
left join  
    TAB_E d on a.IMSI=d.called_imsi 
group by  
    a.IMSI, 
    a.GJ, 
    a.YYS

语法错误string query1 = "SELECT 季度,COUNT(CASE WHEN 季度 = 'Q1' THEN 1 ELSE NULL END) AS Q1Count, COUNT(CASE WHEN 季度 = 'Q2' THEN 1 ELSE NULL END) AS Q2Count,COUNT(CASE WHEN 季度 = 'Q3' THEN 1 ELSE NULL END) AS Q3Count,COUNT(CASE WHEN 季度 = 'Q4' THEN 1 ELSE NULL END) AS Q4Count FROM FAIsum GROUP BY 季度 WHERE 审核年份 = @value1";

你的这条 SQL 查询语句有语法错误。在 GROUP BY 子句之后不能再使用 WHERE 子句。正确的写法应该是把 WHERE 子句移动到 FROM 子句中，使用 INNER JOIN 连接 FAIsum 表和其他表。以下是一个可能的修正版本：

SELECT
  季度,
  COUNT(CASE WHEN 季度 = 'Q1' THEN 1 ELSE NULL END) AS Q1Count,
  COUNT(CASE WHEN 季度 = 'Q2' THEN 1 ELSE NULL END) AS Q2Count,
  COUNT(CASE WHEN 季度 = 'Q3' THEN 1 ELSE NULL END) AS Q3Count,
  COUNT(CASE WHEN 季度 = 'Q4' THEN 1 ELSE NULL END) AS Q4Count
FROM
  FAIsum
  INNER JOIN 其他表 ON ...
WHERE
  审核年份 = @value1
GROUP BY
  季度