Comparing two sqlite databases using Python

问题

I am new in Python. I am trying to compare two sqlite databases having the same schema. The table structure is also same in both db but the data is different. I want to pickup the rows from both tables from both databases which are not present in either db1.fdetail or db2.fdetail

DB1 -

Table - fdetail

id    name    key
1     A       k1
2     B       K2
3     C       K3

DB2 -

Table - fdetail

id    name    keyid
1     A       k1
2     D       K4
3     E       K5
4     F       K6

Expected Output

id    name    keyid
1     B       k2
2     C       K3
3     D       K4
4     E       K5
5     F       K6

My code is

import sqlite3

db1 = r"C:\Users\X\Documents\sqlitedb\db1.db"
db2 = r"C:\Users\X\Documents\sqlitedb\db2.db"

tblCmp = "SELECT * FROM fdetail order by id"

conn1 = sqlite3.connect(db1)
conn2 = sqlite3.connect(db2)

cursor1 = conn1.cursor()
result1 = cursor1.execute(tblCmp)
res1 = result1.fetchall()

cursor2 = conn2.cursor()
result2 = cursor2.execute(tblCmp)
res2 = result2.fetchall()

So I have got two lists res1 and res2. How can I compare the lists based on the column Keyid.

Any help is highly appreciated.

回答1:

If both databases are opened in the same connection (which requires ATTACH), you can do the comparison in SQL:

import sqlite3

db1 = r"C:\Users\X\Documents\sqlitedb\db1.db"
db2 = r"C:\Users\X\Documents\sqlitedb\db2.db"

conn = sqlite3.connect(db1)
conn.execute("ATTACH ? AS db2", [db2])

res1 = conn.execute("""SELECT * FROM main.fdetail
                       WHERE keyid NOT IN
                         (SELECT keyid FROM db2.fdetail)
                    """).fetchall()
res2 = conn.execute("""SELECT * FROM db2.fdetail
                       WHERE keyid NOT IN
                         (SELECT keyid FROM main.fdetail)
                    """).fetchall()

You can also get a single result by combining the queries with UNION ALL.

回答2:

You can use python ‘set’:

res1 = set(res1)
res2 = set(res2)
result = res1.symmetric_difference(res2)

The symmetric difference of two sets is the set of elements which are in one of either set, but not in both.

Or you can iterate over both list respectively check for exists or not.

回答3:

You can convert your lists into sets and use the available set operations to your intents.

来源：https://stackoverflow.com/questions/46867476/comparing-two-sqlite-databases-using-python

标签

python

sqlite