postgresql - how to query using postgres json field where a key is not set? -

postgresql - how to query using postgres json field where a key is not set? -

i can select records match json value where properties->>'foo' = 'bar', if key 'foo' has not yet been set? i've tried where properties->>'foo' null error

no operator matches given name , argument type(s). might need add together explicit type casts. : select "merchants".* "merchants" (properties->>'foo' null)

it's operator precedence issue. is null binds more tightly ->>, code beingness read properties ->> ('foo' null). add together parentheses - (properties ->> 'foo') null.

regress=> select '{"a":1}' ->> 'a'; ?column? ---------- 1 (1 row) regress=> select '{"a":1}' ->> 'b'; ?column? ---------- (1 row) regress=> select '{"a":1}' ->> 'b' null; error: operator not exist: unknown ->> boolean line 1: select '{"a":1}' ->> 'b' null; ^ hint: no operator matches given name , argument type(s). might need add together explicit type casts. regress=> select ('{"a":1}' ->> 'b') null; ?column? ---------- t (1 row)

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