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queryParse.py

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+#!/usr/bin/env python3
+
+import re
+import sqlparse
+
+def parseSQL(SQL):
+    '''
+    Preprocessing the SQL in order to match the operator using re
+    
+    Operator   ReplaceCode
+    >          op0
+    <          op1
+    ==         op2
+    >=         op3
+    <=         op4
+    <>         op5
+    '''
+    SQL = SQL.replace('>=','op3')
+    SQL = SQL.replace('<=','op4')
+    SQL = SQL.replace('<>','op5')
+    SQL = SQL.replace('>','op0')
+    SQL = SQL.replace('<','op1')
+    SQL = SQL.replace('==','op2')
+    '''
+    Operator   ReplaceCode
+    +          op6
+    -          op7
+    *          op8
+    /          op9
+    '''
+    SQL = SQL.replace('+','op6')
+    SQL = SQL.replace('-','op7')
+    SQL = SQL.replace('*','op8')
+    SQL = SQL.replace('/','op9')
+    # print(SQL)
+    '''
+    Step1. Split the SQL into a list
+    This module split the SQL statement into key-value
+    For example: "SELECT id FROM tableA WHERE loan>100000" will parse and split as:
+        [["SELECT": id],
+         ["FROM": tableA],
+         ["WHERE": loan>100000]]
+    '''
+    parsed = sqlparse.parse(SQL)
+    stmt = parsed[0]
+    parsed_list = []
+    for token in stmt.tokens:
+        if token.value != ' ':
+            if token.value.upper().__contains__("WHERE"):
+                parsed_list.append("WHERE")
+                parsed_list.append(token.value[6:])
+            else:
+                parsed_list.append(token.value)
+    # print("Successfully execute step1:")
+    # print(parsed_list)
+    
+    '''
+    Step2. Combine each part to key-value
+
+    Note: this module just for test, only support simple SELECT SQL
+    '''
+    SELECT_KEYWORDS = ['SELECT', 'FROM', 'WHERE', 'ORDER BY']
+    INSERT_KEYWORDS = []
+    UPDATE_KEYWORDS = []
+    DELETE_KEYWORDS = []
+
+    SQL_dict = {}
+    for index in range(len(parsed_list)):
+        if parsed_list[index].upper() in SELECT_KEYWORDS:
+            SQL_dict[parsed_list[index].upper()] = parsed_list[index + 1]
+            index += 1
+    # print("Successfully execute step2:")
+    # print(SQL_dict)
+
+    '''
+    Step3. substract the token.value into operator buffer
+
+    For example: if the select condition is "loan>50000 AND loan<1000000", this condition will parse as:
+        ['loan>50000', 'AND', 'loan<1000000']
+    
+    Above are three subconditions, and we'll substract the subconditions as:
+        [['loan', '>', '50000'], ['AND'], ['loan', '<', '1000000']]
+    
+    Note: this module just for test, only support single table SELECT SQL
+    '''
+    
+    pattern_conj = r'(\s+AND\s+|\s+OR\s+|\s*,\s*|\s*\(\s*|\s*\)\s*)'
+    pattern_op = r'(\s*op1\s*|\s*op2\s*|\s*op3\s*|\s*op4\s*|\s*op5\s*|\s*op6\s*|\s*op7\s*|\s*op8\s*|\s*op9\s*|\s*op0\s*|)'
+    for key in SQL_dict:
+        SQL_dict[key] = re.split(pattern_conj, SQL_dict[key])
+        value = []
+        for tuple in SQL_dict[key]:
+            tuple = re.split(pattern_op, tuple)
+            if tuple != ['']:
+                value.append(tuple)
+        SQL_dict[key] = value
+
+    # print("Successfully execute step3:")
+    # for key in SQL_dict:
+        # print("keywords: " + key)
+        # print(SQL_dict[key])
+
+    return SQL_dict
+
+
+if __name__ == '__main__':
+    res = parseSQL("SELECT ID,AVG(DEPOSIT),MAX(LOAN1) FROM TABLE")
+    print(res)