Answer by Schwern for Hi! Can someone please help me figure out why and how this query works? I can't understand the logic behind it. Thanks so much

You have to read it from the outside in. It helps to space it all out.

TRIM(  leading '(' FROM     LEFT(      location,       POSITION(',' IN location) - 1    ))

POSITION(',' IN location) returns the offset of the first , in location. In your example (37.709725805163, -122.413623946206) that's 17. Subtracting one excludes the comma, 16.

LEFT(location, POSITION(',' IN location) - 1) evaluates in your example to left(location, 16) and returns everything in location which is left of the given position: first , except the comma. (37.709725805163.

Finally TRIM( leading '(' from LEFT(location, POSITION(',' IN location) - 1)) evaluates to TRIM( leading '(' from (37.709725805163) and removes everything from the string before and including the first '('. 37.709725805163.

You should be able to figure out the second one.