如何从查询结果中将一行中的单元格设为空白？

Posted 2023-04-18

【中文标题】如何从查询结果中将一行中的单元格设为空白？

【英文标题】：How to make a cell blank in a row from a query result?

【发布时间】：2016-11-03 23:07:21

【问题描述】：

我有一个查询如下：

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') 

上面的查询在执行时会返回以下结果：

我需要将结果显示如下：

“Chain_Id”列是“整数”类型，我怎样才能将其设为空白？

【参考方案1】：

你可以简单地选择 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)

【讨论】：

如果我选择 NULL，我会得到一个错误。我正在使用 SQL Workbench 来测试查询。

我已经更新了 asnwer .. 希望清晰有用

@Newbee：在 Informix 中，您需要指定 null 的类型——例如NULL::INTEGER — 而不是只使用普通的 NULL，它可以是任何类型。如果您愿意，也可以使用CAST(NULL AS INTEGER)。

【参考方案2】：

在 Informix 中，您可以在投影列表中使用 NULL，但列必须具有类型。由于在 Informix 中 NULL 没有类型，因此您需要使用 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)。

【参考方案3】：

一种方法是转换为NULL：

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

另一个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