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Translate NULLIF #596
Description
NULLIF(value1, value2)The
NULLIFfunction returns anullvalue ifvalue1equalsvalue2; otherwise it returnsvalue1. This can be used to perform the inverse operation of theCOALESCEexample given above:SELECT NULLIF(value, '(none)') ...In this example, if
valueis(none),nullis returned, otherwise the value ofvalueis returned.
- Translate as extensions on
DbFunctions:
public static T NullIf<T>(this DbFunctions _, T a, T b) where T : class
=> Equals(a, b) ? default(T) : a;
public static T? NullIf<T>(this DbFunctions _, T? a, T? b) where T : struct
=> Equals(a, b) ? default(T?) : a;- Consider translating simple ternary expressions:
a == b ? default(T) : a;
a == b ? default(T?) : a;Compatibility
Available for PostgreSQL 7.4 or later.
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roji commentedon Aug 15, 2018
Don't you have it backwards in your implementation above? Shouldn't it be
a == b ? null : a?Otherwise I like it... If we can get the ternary version to work well that would be great, but mind null vs. default... This could get a bit tricky.
roji commentedon Dec 11, 2024
@WhatzGames can you please comment here so you can be assigned for credit?
Add NullIf Translation for Ternary expressions (#3403)
WhatzGames commentedon Dec 11, 2024
Sure! And thanks for the cleanup :)
roji commentedon Dec 12, 2024
After a second look, NULLIF is actually universally supported across databases and an issue already exists to track doing this in EF itself: dotnet/efcore#31682. So when I have a spare moment, I'll port this support into EF and remove it from EFCore.PG.
Add NullIf Translation for Ternary expressions (npgsql#3403)