blocks|key|1693847|text|要么使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1693848|SELECT+IF(field1+IS+NULL+or+field1+=+'',+'empty',+field1)+as+field1+
from+tablename|code-block|syntax|javascript|1693849|或|1693850|SELECT+case+when+field1+IS+NULL+or+field1+=+''
++++++++++++then+'empty'
++++++++++++else+field1
+++++++end+as+field1+
from+tablename|1693851|如果您只想检查null而不是空字符串，那么您也可以使用ifnull()或coalesce(field1,+'empty')。但这不适用于空字符串。|offset|length|style|CODE|1693852|entityMap^0|0|0|0|0|7|4|R|8|10|P|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@$M|X|N|Y|O|P]|$M|Z|N|10|O|P]|$M|11|N|12|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|R|$]]

Either use

<pre><code>SELECT IF(field1 IS NULL or field1 = '', 'empty', field1) as field1 
from tablename
</code></pre>

or

<pre><code>SELECT case when field1 IS NULL or field1 = ''
 then 'empty'
 else field1
 end as field1 
from tablename
</code></pre>

If you only want to check for <code>null</code> and not for empty strings then you can also use <code>ifnull()</code> or <code>coalesce(field1, 'empty')</code>. But that is not suitable for empty strings.

blocks|key|1907485|text|或者，您也可以使用CASE来执行相同的操作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1907486|SELECT+CASE+WHEN+field1+IS+NULL+OR+field1+=+''+
+++++++THEN+'empty'+
+++++++ELSE+field1+END+AS+field1
FROM+tablename.|code-block|syntax|javascript|1907487|entityMap^0|9|4|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Alternatively you can also use <code>CASE</code> for the same:

<pre><code>SELECT CASE WHEN field1 IS NULL OR field1 = '' 
 THEN 'empty' 
 ELSE field1 END AS field1
FROM tablename.
</code></pre>

blocks|key|1907556|text|如果你想签入PHP，那么你应该这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1907557|$query_s+=mysql_query("SELECT+YOURROWNAME+from+`YOURTABLENAME`+where+name+=+$name");
$ertom=mysql_fetch_array($query_s);
if+(''+!==+$ertom['YOURROWNAME'])+{
++//do+your+action
++echo+"It+was+filled";
}+else+{+
++echo+"it+was+empty!";
}|code-block|syntax|javascript|1907558|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you would like to check in PHP , then you should do something like : 

<pre><code>$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!";
}
</code></pre>

blocks|key|1694071|text|SELECT+*+FROM+(+
++++SELECT++2+AS+RTYPE,V.ID+AS+VTYPE,+DATE_FORMAT(ENTDT,+''%25d-%25m-%25Y'')++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|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1694072|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>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)&gt;0,(DR_CR),0),0) AS DR ,ROUND(IF((DR_CR)&lt;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&gt;=''',FROMDATE ,''' AND t.entdt&lt;=''',TODATE ,''' ',VTYPE,'
 ORDER BY CAST(ENTDT AS DATE)) AS ta
</code></pre>

blocks|key|1694142|text|您可以创建一个函数来简化此操作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1694143|create+function+IFEMPTY(s+text,+defaultValue+text)
returns+text+deterministic
return+if(s+is+null+or+s+=+'',+defaultValue,+s);|code-block|syntax|javascript|1694144|使用：|1694145|SELECT+IFEMPTY(field1,+'empty')+as+field1+
from+tablename|1694146|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You can create a function to make this easy.

<pre><code>create function IFEMPTY(s text, defaultValue text)
returns text deterministic
return if(s is null or s = '', defaultValue, s);
</code></pre>

Using:

<pre><code>SELECT IFEMPTY(field1, 'empty') as field1 
from tablename
</code></pre>

blocks|key|1907678|text|您可以在IF中使用the+IFNULL+function。这会稍微短一点，字段名称的重复项也会更少。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1907679|SELECT+IF(IFNULL(field1,+'')+=+'',+'empty',+field1)+AS+field1+
FROM+tablename|code-block|syntax|javascript|1907680|entityMap|0|LINK|mutability|MUTABLE|url|https://www.w3schools.com/sql/func_mysql_ifnull.asp^0|4|2|D|6|9|J|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

You can use <a href="https://www.w3schools.com/sql/func_mysql_ifnull.asp" rel="noreferrer">the <code>IFNULL</code> function</a> inside the <code>IF</code>. This will be a little shorter, and there will be fewer repetitions of the field name.

<pre><code>SELECT IF(IFNULL(field1, '') = '', 'empty', field1) AS field1 
FROM tablename
</code></pre>

blocks|key|1907689|text|尝试使用nullif|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1907690|SELECT+ifnull(nullif(field1,''),'empty')+AS+field1
++FROM+tablename;|code-block|syntax|javascript|1907691|entityMap^0|4|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Try using <code>nullif</code>:

<pre><code>SELECT ifnull(nullif(field1,''),'empty') AS field1
 FROM tablename;
</code></pre>

blocks|key|1907794|text|通过修剪和比较，我们确保还会注意字段中的空字符、制表符或空格字符内容。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1907795|SELECT
++++CASE
++++++++WHEN+LTRIM(RTRIM(col_1))=''+or+col_1+IS+NULL+THEN+'Not+available'
++++++++ELSE+col_1
++++END+AS+col_alias
FROM
++++my_table|code-block|syntax|javascript|1907796|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

By trimming and comparing, we ensure we also take care of empty or tab or space character content in the field.
<pre><code>SELECT
 CASE
 WHEN LTRIM(RTRIM(col_1))='' or col_1 IS NULL THEN 'Not available'
 ELSE col_1
 END AS col_alias
FROM
 my_table
</code></pre>

I am trying to figure out how to check if a field is <code>NULL</code> or empty. I have this:
<pre><code>SELECT IFNULL(field1, 'empty') as field1 from tablename
</code></pre>
I need to add an additional check <code>field1 != &quot;&quot;</code> something like:
<pre><code>SELECT IFNULL(field1, 'empty') OR field1 != &quot;&quot; as field1 from tablename
</code></pre>
Any idea how to accomplish this?

How to check if field is null or empty in MySQL?

我正在尝试弄清楚如何检查一个字段是NULL还是空。我有这个：SELECT IFNULL(field1, 'empty') as field1 from tablename我需要添加一个额外的检查field1 != ""，如下所示：SELECT IFNULL(field1, 'empty') OR field1 != "...

问如何检查MySQL中的字段是否为null或空？
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问如何检查MySQL中的字段是否为null或空？
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