如何从查询结果中让一行中的单元格空白？

Question

我有如下疑问：

SELECT 
     cc.chain_desc as chain_desc 
    ,cc.chain_id as chain_id 
    ,COUNT(distinct t.trans_id) as TranCount
FROM TRANSACTION AS t 
LEFT OUTER JOIN location AS l 
ON t.location_id = l.location_id 
LEFT OUTER JOIN trans_line AS tl 
ON t.trans_id = tl.trans_id 
LEFT OUTER JOIN contract as c 
ON t.contract_id = c.contract_id 
LEFT OUTER JOIN chain_desc as cc 
ON l.chain_id = cc.chain_id 
WHERE 
t.loc_country = 'U' 
AND c.issuer_id IN (156966,166203) 
AND t.trans_date >= '2016-10-01 00:00' 
and t.trans_date < '2016-10-31 00:00'
AND tl.cat NOT IN ('DEF','DEFD','DEFC') 
GROUP BY cc.chain_desc, cc.chain_id 


UNION 

SELECT 
    'TOTAL'
    ,0
    ,COUNT(distinct t.trans_id) 
FROM TRANSACTION AS t 
LEFT OUTER JOIN location AS l 
ON t.location_id = l.location_id 
LEFT OUTER JOIN trans_line AS tl 
ON t.trans_id = tl.trans_id 
LEFT OUTER JOIN contract as c 
ON t.contract_id = c.contract_id 
LEFT OUTER JOIN chain_desc as cc 
ON l.chain_id = cc.chain_id 
WHERE 
t.loc_country = 'U' 
AND c.issuer_id IN (156966,166203) 
AND t.trans_date >= '2016-10-01 00:00' 
and t.trans_date < '2016-10-31 00:00'
AND tl.cat NOT IN ('DEF','DEFD','DEFC')

以上查询执行后返回以下结果：

我需要显示如下结果：

"Chain_Id" 列是 "integer" 类型，我怎样才能把它留空？。

Answer 1

一种方法是转换为 NULL:

    (case when cc.chain_id <> 0 then cc.chain_id end) as chain_id

另一种是将所有内容都转换为字符串：

    (case when cc.chain_id <> 0 then cast(cc.chain_id as varchar(255)) else '' end) as chain_id

Answer 2

你可以简单地 select null

 .....

 UNION 

SELECT 
    'TOTAL'
    , NULL::INTEGER
    ,COUNT(distinct t.trans_id) 
FROM TRANSACTION AS t 
LEFT OUTER JOIN location AS l 
ON t.location_id = l.location_id 
LEFT OUTER JOIN trans_line AS tl 
ON t.trans_id = tl.trans_id 
LEFT OUTER JOIN contract as c 
ON t.contract_id = c.contract_id 
LEFT OUTER JOIN chain_desc as cc 
ON l.chain_id = cc.chain_id 
WHERE 
t.loc_country = 'U' 
AND c.issuer_id IN (156966,166203) 
AND t.trans_date >= '2016-10-01 00:00' 
and t.trans_date < '2016-10-31 00:00'
AND tl.cat NOT IN ('DEF','DEFD','DEFC')

因为 null 不是您可以尝试在第一个查询上方添加的类型

DEFINE test INT;
LET test = NULL;


......

SELECT 
    'TOTAL'
    , test
    ,COUNT(distinct t.trans_id) 
    .....

或者像@Jonathan Leffler 建议的那样使用 NULL::INTEGER 或 CAST(NULL AS INTEGER)

Answer 3

在 Informix 中，您可以在投影列表中使用 NULL，但该列必须具有类型。由于在 Informix NULL 中没有类型，您需要使用 CAST.

SELECT NULL::INTEGER AS id FROM systables WHERE tabid = 1;

SELECT CAST(NULL AS INTEGER) AS id FROM systables WHERE tabid = 1;

您可以查看其他问题的答案 (Informix: Select null problem)。

您可以查看 IBM 知识中心 (NULL Keyword)。

如何从查询结果中让一行中的单元格空白？

How to make a cell blank in a row from a query result?

sql

informix