16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
65 lines
1.3 KiB
Plaintext
65 lines
1.3 KiB
Plaintext
== Why is this an issue?
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Under the covers, Simple ``++CASE++`` expressions are evaluated as searched ``++CASE++`` expressions. That is,
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----
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CASE @foo
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WHEN 1 THEN 'a'
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WHEN 2 THEN 'b'
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----
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is actually evaluated as
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----
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CASE
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WHEN @foo = 1 THEN 'a'
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WHEN @foo = 2 THEN 'b'
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----
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In most situations the difference is inconsequential, but when the input expression isn't fixed, for instance if ``++RAND()++`` is involved, it is likely to yield unexpected results. For that reason, it is better to evaluate the input expression once, assign it to a variable, and use the variable as the ``++CASE++``'s input expression.
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This rule raises an issue when any of the following is used in a ``++CASE++`` input expression: ``++RAND++``, ``++NEWID++``, ``++CRYPT_GEN_RANDOM++``.
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=== Noncompliant code example
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[source,sql]
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----
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CASE CONVERT(SMALLINT, RAND()*@foo) -- Noncompliant
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WHEN 1 THEN 'a'
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WHEN 2 THEN 'b'
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----
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=== Compliant solution
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[source,sql]
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----
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DECLARE @bar SMALLINT = CONVERT(SMALLINT, RAND()*@foo)
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CASE @bar
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WHEN 1 THEN 'a'
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WHEN 2 THEN 'b'
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Assign this "CASE" input expression to a variable so that it's executed only once, and evaluate the variable instead.
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=== Highlighting
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the case input expression
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endif::env-github,rspecator-view[]
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