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POhow can I include a NULL value using array_agg in postgresql?
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16752425
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2013-05-25T18:00:18.833
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2013-05-25T18:46:28.747
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If I query this : <pre><code>SELECT DISTINCT class_low FROM groups NATURAL JOIN species WHERE type ~~ 'faune' AND class_high ~~ 'Arachnides' AND (class_middle ~~ 'Araignées' OR class_middle IS NULL) AND (class_low ~~ '%' OR class_low IS NULL); </code></pre> I get : <pre><code> class_low --------------------- Dictynidés Linyphiidés Sparassidés Metidés Thomisidés Dolomedidés Pisauridés Araignées sauteuses Araneidés Lycosidés Atypidés Pholcidés Ségestriidés Tetragnathidés Miturgidés Agelenidés </code></pre> Notice the NULL value (it's not a empty varchar). now if I query like that : <pre><code>SELECT array_to_string(array_agg(DISTINCT class_low), ',') FROM groups NATURAL JOIN species WHERE type ~~ 'faune' AND class_high ~~ 'Arachnides' AND (class_middle ~~ 'Araignées' OR class_middle IS NULL) AND (class_low ~~ '%' OR class_low IS NULL); </code></pre> I get : <pre><code> array_to_string ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Agelenidés,Araignées sauteuses,Araneidés,Atypidés,Dictynidés,Dolomedidés,Linyphiidés,Lycosidés,Metidés,Miturgidés,Pholcidés,Pisauridés,Ségestriidés,Sparassidés,Tetragnathidés,Thomisidés </code></pre> The NULL value is not inserted. Is there any way to include it ? I mean having something like : ...,,... (just a double colon)
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<sql><arrays><postgresql><aggregate-functions><postgresql-8.4>
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how can I include a NULL value using array_agg in postgresql?
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