my_string = "SELECT * FROM users WHERE first_name = 'first name value'"
my_string2 = "SELECT * FROM users WHERE first_name = 'first\"s name value'"
my_string3 = "SELECT * FROM users WHERE first_name = 'first\\'s name value'"
 
rx = /first_name = (['"])((?:(?!\1)[^\\])*(?:\\.(?:(?!\1)[^\\])*)*)\1/i
 
puts rx.match my_string      # => first_name = 'first name value'
puts rx.match(my_string)[2]  # => first name value
puts rx.match my_string2     # => first_name = 'first"s name value'
puts rx.match(my_string2)[2] # => first"s name value
puts rx.match my_string3     # => first_name = 'first\'s name value'
puts rx.match(my_string3)[2] # => first\'s name value

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