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[#2660] Add some documentation about jOOQ not supporting operator

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precedence
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Lukas Eder 2013-08-15 13:34:41 +02:00
parent 08aa25a872
commit 3d050f8106
1 changed files with 32 additions and 1 deletions
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33
jOOQ-website/src/main/resources/manual-3.2.xml
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@ -3975,7 +3975,15 @@ Field<Integer> field2 = val("1").coerce(Integer.class);]]></java>
You can write something like this in jOOQ:
</p>
<java>create.select(val(1).add(2).mul(val(5).sub(3)).div(2).mod(10);</java>
<java>create.select(val(1).add(2).mul(val(5).sub(3)).div(2).mod(10));</java>
<h3>Operator precedence</h3>
<p>
jOOQ does not know any operator precedence (see also <reference id="boolean-operator-precedence" title="boolean operator precedence"/>). All operations are evaluated from left to right, as with any object-oriented API. The two following expressions are the same:
</p>
<java> val(1).add(2) .mul(val(5).sub(3)) .div(2) .mod(10);
(((val(1).add(2)).mul(val(5).sub(3))).div(2)).mod(10);</java>
<h3>Datetime arithmetic expressions</h3>
<p>
@ -5076,6 +5084,29 @@ BOOK.TITLE.notEqualIgnoreCase("animal farm")]]></java>
</code-pair>
</content>
</section>
<section id="boolean-operator-precedence">
<title>Boolean operator precedence</title>
<content>
<p>
As previously mentioned in the manual's section about <reference id="arithmetic-expressions" title="arithmetic expressions"/>, jOOQ does not implement operator precedence. All operators are evaluated from left to right, as expected in an object-oriented API. This is important to understand when combining <reference id="boolean-operators" title="boolean operators"/>, such as <code>AND</code>, <code>OR</code>, and <code>NOT</code>. The following expressions are equivalent:
</p>
<java>
A.and(B) .or(C) .and(D) .or(E)
(((A.and(B)).or(C)).and(D)).or(E)
</java>
<p>
In SQL, the two expressions wouldn't be the same, as SQL natively knows operator precedence.
</p>
<sql>
A AND B OR C AND D OR E -- Precedence is applied
(((A AND B) OR C) AND D) OR E -- Precedence is overridden
</sql>
</content>
</section>
<section id="comparison-predicate-degree-n">
<title>Comparison predicate (degree > 1)</title>