python – Capture the WHERE clause of an SQL query

Question:

I need to capture only the where clause of several queries to analyze the filters used. For example:

select "DIM_1"."col1",
"DIM_2"."col2" ,
"DIM_3"."col3" , 
"DIM_4"."col4" , 
"FAT_1"."col5"     
from "FAT_1",
 "DIM_1",
 "DIM_2",
 "DIM_3",
 "DIM_4"
where  "DIM_1"."col1" IS NOT NULL 
AND "DIM_2"."col2" LIKE ('SUCCESS')
AND "DIM_3"."col3" BETWEEN 20161213 AND 20161222
AND "DIM_4"."col4" > 0

I created a list with SQL, and then I tried to apply regular expressions to extract the where part, but without success, here's what I tried:

`for line in sql:`
    `if re.search(r'[where]\W',line):`
        `where.append(line)`

Unfortunately I couldn't extract only the where part, can you tell me what mistake I made and how to fix it?

Answer:

I believe that what you want is to get the where clauses.

First let's check what can come after the where command.

where post-following commands

According to postgres .
I only sell the most common

  • GROUP BY
  • HAVING
  • ORDER BY
  • LIMIT
  • OFFSET
  • "NADA" – Because it can be just the where without any subsequent command.

REGEX

  • pattern : (?<=where)(.*?)((ORDER BY|GROUP BY|HAVING|LIMIT|OFFSET|$).*)
  • flags : si

Explanation

  • (?<=where) – ensures that what we are searching for comes after where
  • (.*?) – everything that follows will be the clauses.
  • ((ORDER BY|GROUP BY|HAVING|LIMIT|OFFSET|$).*) – guarantees that it will end at one of the commands or at the end( $ ).
  • Flag : s – says that the . (dot) must include \n in the search.
  • Flag : i – case-insensitive – allows you to search for uppercase or lowercase.

Examples

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