How to detect and use the row number of a table in postgreSQL, using Python?

Question

I'm trying to find a way to use the row number of a table in postgreSQL, using Python. So in a for loop, when the table row number is 22, do something.

Let me show you an easy example:

conn = psycopg2.connect(database=DB_NAME, user=DB_USER, password=DB_PASS, host=DB_HOST, port=DB_PORT)
cur = conn.cursor()

cur.execute("SELECT a, b FROM table")
rows = cur.fetchall()

for data in rows:
    if data.row_number == 22:`    #if the table row number is 22...
        do something

obviously the expression "data.row_number" does not exist and produces an error...

Somebody could help me?

Thanks

Answer 1

You could try with the ROW_NUMBER() function, for example:

conn = psycopg2.connect(database=DB_NAME, user=DB_USER, password=DB_PASS, host=DB_HOST, port=DB_PORT)
cur = conn.cursor()

cur.execute("SELECT a, b, ROW_NUMBER () OVER (ORDER BY a) FROM table")
rows = cur.fetchall()

for data in rows:
    if data[2] == 22:    #if the table row number is 22...
        # do something

Answer 2

simple solution is using the enumerate :

for row_number, data in enumerate(rows, 1):
    if row_number == 22:

Answer 3

您可以从文档中尝试ROW_NUMBER()方法