blocks|key|2526843|text|您可以使用CASE+WHEN|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2526844|SELECT+CASE+WHEN+MATCH_EXISTS+=+0+THEN+0
++++++++++++ELSE+1
+++++++END+AS+MATCH_EXISTS+
FROM+(SELECT+COUNT(*)+AS+MATCH_EXISTS+
++++++FROM+MY_TABLE+
++++++WHERE+MY_COLUMN+IS+NOT+NULL)+AS+t;|code-block|syntax|javascript|2526845|编辑：|BOLD|2526846|SELECT+CASE+WHEN+COUNT(*)+=+0+THEN+0
++++++++++++ELSE+1
++++++++END+as+MATCH_EXISTS+
FROM+MY_TABLE+
WHERE+MY_COLUMN+IS+NOT+NULL;|2526847|entityMap^0|5|9|0|0|0|3|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|U|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|V|8|@$9|W|A|X|B|M]]|D|@]|E|$]]|$1|N|3|O|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|P|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|Q|$]]

You can use <code>CASE WHEN</code>:

<pre><code>SELECT CASE WHEN MATCH_EXISTS = 0 THEN 0
 ELSE 1
 END AS MATCH_EXISTS 
FROM (SELECT COUNT(*) AS MATCH_EXISTS 
 FROM MY_TABLE 
 WHERE MY_COLUMN IS NOT NULL) AS t;
</code></pre>

EDIT:

<pre><code>SELECT CASE WHEN COUNT(*) = 0 THEN 0
 ELSE 1
 END as MATCH_EXISTS 
FROM MY_TABLE 
WHERE MY_COLUMN IS NOT NULL;
</code></pre>

blocks|key|2994168|text|这应该是最快的。最多只能排一排。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2994169|SELECT+COUNT(*)+AS+MATCH_EXISTS
FROM+MY_TABLE+
WHERE+MY_COLUMN+IS+NOT+NULL
++AND+rownum+<=+1;|code-block|syntax|javascript|2994170|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|$]]

This should be fastest... get at most one row.

<pre><code>SELECT COUNT(*) AS MATCH_EXISTS
FROM MY_TABLE 
WHERE MY_COLUMN IS NOT NULL
 AND rownum &lt;= 1;
</code></pre>

blocks|key|1454447|text|如果您使用exists子句，那么对于大型表来说，这会更快，因为Oracle不需要扫描整个表。一旦有一行，它就可以停止检索它：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1454448|select+count(*)+as+match_exists
from+dual
where+exists+(select+*+
++++++++++++++from+my_table+
++++++++++++++where+my_column+is+not+null);|code-block|syntax|javascript|1454449|entityMap^0|5|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|$]]

If you use an <code>exists</code> clause this should be faster for large tables because Oracle doesn't need to scan the whole table. As soon as there is one row, it can stop retrieving it:

<pre><code>select count(*) as match_exists
from dual
where exists (select * 
 from my_table 
 where my_column is not null);
</code></pre>

blocks|key|2526935|text|不要做count()。为了提高性能，请使用exists|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2526936|select+(case+when+exists+(select+1+as+MATCH_EXISTS+
++++++++++++++++++++++++++from+MY_TABLE+
++++++++++++++++++++++++++where+MY_COLUMN+is+not+null
+++++++++++++++++++++++++)
++++++++++++++then+1+else+0
++++++++end)
from+dual;|code-block|syntax|javascript|2526937|这可以大大加快速度。|2526938|entityMap^0|3|7|L|6|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

Don't do a <code>count()</code>. For performance, use <code>exists</code>:

<pre><code>select (case when exists (select 1 as MATCH_EXISTS 
 from MY_TABLE 
 where MY_COLUMN is not null
 )
 then 1 else 0
 end)
from dual;
</code></pre>

This can be significantly faster.

I'm using Oracle and I want to turn the result from a select count into a "binary" 0/1 value ... 0 = 0 ... non-zero = 1. From what I read online, in MS SQL, you can cast it to a "bit" but Oracle doesn't appear to support that.

Here's my simple example query (the real query is much more complex). I want MATCH_EXISTS to always be 0 or 1. Is this possible?

<pre><code>select count(*) as MATCH_EXISTS 
from MY_TABLE 
where MY_COLUMN is not null;
</code></pre>

Oracle SQL - convert select count(*) into zero or one

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我使用Oracle，并希望将选择计数的结果转换为“二进制”0/1值.0=0.非零= 1。根据我在网上看到的，在MS中，您可以将其转换为“位”，但Oracle似乎不支持这一点。下面是我的简单示例查询(真正的查询要复杂得多)。我希望MATCH_EXISTS总是0或1，这有可能吗？select count(*) as MAT...

问Oracle SQL -将选择的计数(*)转换为0或1
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问Oracle SQL -将选择的计数(*)转换为0或1EN