Compare two columns in SQL - sql

Question

I'm new to SQL and have very basic queries in GCP.
Let's consider this table below:
Name
B
C
Arun
1234-5678
1234
Tara
6789 - 7654
6789
Arun
4567
4324
Here, I want to compare column B and C and if they match then give 1 else 0 in column same and else different (which we have to create).
So here the catch:
if column B has 1234-5678 and column C has 1234, then the column should match considering only the number before the "-" in the value.
The output should be :
Name
B
C
same
different
Arun
1234-5678
1234
1
0
Tara
6789 - 7654
6789
1
0
Arun
4567
4324
0
1
Also, I want to count the values of 1 for each values in Name for same and different columns.
So far I've tried this:
SELECT
name,
b,
c ,
if(b = c, 1, 0) as same,
if (b!=c,1,0) as different,
count(same),
count(different)
From Table

Answer 1

using "MySQL" (will work almost same with SQL server as well) here's the possible solution.
Step 1) Setup table
CREATE TABLE Users (
Name varchar(50),
B varchar(50),
C varchar(50)
);
INSERT INTO Users
VALUES
('Arun', '1234-5678', '1234'),
('Tara', '6789-7654', '6789'),
('Arun', '4567', '4324');
Step 2) same & different columns
SELECT
Name, B, C,
CASE WHEN SUBSTRING_INDEX(B, "-", 1) = C THEN 1 ELSE 0 END as same,
CASE WHEN SUBSTRING_INDEX(B, "-", 1) <> C THEN 1 ELSE 0 END as different
FROM
Users
Step 3) Join both results to get total_same & total_different for each user
SELECT
Name,
SUM(CASE WHEN SUBSTRING_INDEX(B, "-", 1) = C THEN 1 ELSE 0 END) as total_same,
SUM(CASE WHEN SUBSTRING_INDEX(B, "-", 1) <> C THEN 1 ELSE 0 END) as total_different
FROM
Users
GROUP BY Name
Reference: SQL Fiddle

Answer 2

For the first step, you will need to SUBSTR the column b.
We start at position 1 and we want 4 characters (only works if there's only 4 characters before the '-').
With table2 as (
select name, b,c, same, different from (select name, b, c, case when (SUBSTR(b,1,4) = c)
then '1' else '0' end as same, case when(SUBSTR(b,1,4)!= c) then '1' else '0' end as different
from Table1
group by name, b,c))
The WITH clause can be used when you have complex query, and if you want to create a temporary table in order to use it after.
The Table2 give you this :
After the WITH clause, you will have the second step, the count of same / different per name :
Select table1.name,count(table2.same+table2.different) as total from table1
join table2 on (table2.name = table1.name and table2.b = table1.b)
group by table1.name;
The output give you the total per name (the name are group by, so in your example you will only have 2 rows, one for Arun with a total of 2 (same + different) and the other one with a total of 1)
So here's the entire code :
with table2 as (
select name, b,c, same, different from (select name, b, c, case when (SUBSTR(b,1,4) = c) then '1' else '0' end as same, case when(SUBSTR(b,1,4)!= c) then '1' else '0' end as different
From Table1
group by name, b,c))
select table1.name, table1.b, table1.c, count(table2.same+table2.different) as total from table1
join table2 on (table2.name = table1.name and table2.b = table1.b)
group by table1.name;