如何检查字段为空或空mysql？

Question

我想弄清楚如何检查一个字段为空或空。我有这个

SELECT IFNULL(field1, 'empty') as field1 from tablename. 

我需要添加额外的检查字段1！=“”像

SELECT IFNULL(field1, 'empty') OR field1 != "" as field1 from tablename. 

任何想法如何做到这一点？

Answer 1

要么使用

SELECT IF(field1 IS NULL or field1 = '', 'empty', field1) as field1 
from tablename 

或

SELECT case when field1 IS NULL or field1 = '' 
      then 'empty' 
      else field1 
     end as field1 
from tablename 

如果你只是想检查null而不是为空字符串，那么你也可以使用ifnull你尝试过。但是这也不适合空串。

Answer 2

另外，您还可以使用CASE为同：

SELECT CASE WHEN field1 IS NULL OR field1 = '' 
     THEN 'empty' 
     ELSE field1 END AS field1 
FROM tablename. 

Answer 3

如果你想在PHP检查，那么你应该这样做：

$query_s =mysql_query("SELECT YOURROWNAME from `YOURTABLENAME` where name = $name"); 
$ertom=mysql_fetch_array($query_s); 
if ('' !== $ertom['YOURROWNAME']) { 
    //do your action 
    echo "It was filled"; 
} else { 
    echo "it was empty!"; 
} 

Answer 4

SELECT * FROM ( 
    SELECT 2 AS RTYPE,V.ID AS VTYPE, DATE_FORMAT(ENTDT, ''%d-%m-%Y'') AS ENTDT,V.NAME AS VOUCHERTYPE,VOUCHERNO,ROUND(IF((DR_CR)>0,(DR_CR),0),0) AS DR ,ROUND(IF((DR_CR)<0,(DR_CR)*-1,0),2) AS CR ,ROUND((dr_cr),2) AS BALAMT, IF(d.narr IS NULL OR d.narr='''',t.narration,d.narr) AS NARRATION 
    FROM trans_m AS t JOIN trans_dtl AS d ON(t.ID=d.TRANSID) 
    JOIN acc_head L ON(D.ACC_ID=L.ID) 
    JOIN VOUCHERTYPE_M AS V ON(T.VOUCHERTYPE=V.ID) 
    WHERE T.CMPID=',COMPANYID,' AND d.ACC_ID=',LEDGERID ,' AND t.entdt>=''',FROMDATE ,''' AND t.entdt<=''',TODATE ,''' ',VTYPE,' 
    ORDER BY CAST(ENTDT AS DATE)) AS ta 

Answer 5

您可以创建一个简单的功能。

create function IFEMPTY(s text, defaultValue text) 
returns text deterministic 
return if(s is null or s = '', defaultValue, s); 

使用：

SELECT IFEMPTY(field1, 'empty') as field1 
from tablename