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Through Python, I'm pulling data from a JSON request and inserting into a database, but I want to make sure those records do not already exist before inserting it in there.

I know similar questions have been asked before, but mine is different because mine is not querying from a second table. So how do I approach this?

What I've tried, and I get an incorrect Syntax error, is 

INSERT INTO table (col1, col2, col3) 
VALUES (val1, val2, val3) 
WHERE NOT EXISTS (select col1 FROM table WHERE col1 != val1)

Can anyone give me a better way to approach this problem? Thank you.

Magnus
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Emac
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2 Answers2

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IF NOT EXISTS(SELECT ...)
  INSERT ... VALUES ...
Tab Alleman
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  • Thanks! I got it to work using this (in case anyone else runs into this problem and needs further clarification) IF NOT EXISTS (SELECT col1 FROM table WHERE col1 = val1) INSERT INTO col1, col2, col3 VALUES val1, val2, val3 – Emac Nov 30 '17 at 19:21
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You can also do something like this:

INSERT INTO table (col1, col2, col3) 
SELECT val1, val2, val3
WHERE NOT EXISTS (SELECT 0 FROM table WHERE col1 = val1)

Note how SELECT is not selecting from a table. It simply returns one row (val1, val2, val3) if the condition holds and zero rows if it doesn't.

BTW, you can write that more succinctly as...

INSERT INTO table (col1, col2, col3) 
SELECT val1, val2, val3
WHERE val1 NOT IN (SELECT col1 FROM table)

...but beware that in the presence of NULLs, this is not the exact equivalent.

Branko Dimitrijevic
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