Insert when NOT matched - T/SQL - sql

Question

I have 3 tables with same 5 columns (+ 1 flag column in T2 which we will use later...let's focus on 5 columns for this example).
T1, T2, and T3.
1st column in all three tables are Key Columns.
Let's say there are 5 records in T1 and T2.
4 records in T1 and T2 match for all columns.
5th record has 4 matching columns (1 key + 3 non-key). This means, T1 and T2 has 1 non-matching non-key column for the 5th record.
I want to do nothing with the first 4 columns
I want to insert the 5th column from T2 to T3 and update the 6th column of T2 to TRUE.
How does one go about doing this? Merge query won't work as it works with 2 tables only as far as I know...correct me if I am wrong.
Just a note: these tables have actually over 100 columns (same columns) sooo...hehe
ThanX
UPDATE: I wish to still pass the values for the first 4 columns from T2 to T3...not just the column that changed.

Answer 1

-- Not tuned to any particular syntax, may need to be tweaked.
T1([a],b,c,d,e);
T2([a],b,c,d,e,f);
T3([a],b,c,d,e);
---------
-- SQL --
---------
BT;
INSERT INTO T3
SELECT
T2.a,
CASE WHEN (T1.b <> T2.b) THEN T2.b ELSE null,
CASE WHEN (T1.c <> T2.c) THEN T2.c ELSE null,
CASE WHEN (T1.d <> T2.d) THEN T2.d ELSE null,
CASE WHEN (T1.e <> T2.e) THEN T2.e ELSE null
FROM
T1,
T2
WHERE T1.a = T2.a
AND (
T1.b <> T2.b
OR T1.c <> T2.c
OR T1.d <> T2.d
OR T1.e <> T2.e
);
UPDATE T2
SET T2.f = true
T1.a IN (
SEL T1.a
FROM T1, T2
WHERE T1.a = T2.a
AND (
T1.b <> T2.b
OR T1.c <> T2.c
OR T1.d <> T2.d
OR T1.e <> T2.e
)
);
ET; -- OR COMMIT depending on sytax
EXAMPLE DATA
-- BEFORE -- -- AFTER --
T1 T1
|[a]| b | c | d | e | |[a]| b | c | d | e |
|---+---+---+---+---| |---+---+---+---+---|
| 0 | 1 | 2 | 3 | 4 | | 0 | 1 | 2 | 3 | 4 |
| 1 | 2 | 3 | 4 | 5 | | 1 | 2 | 3 | 4 | 5 |
| 1 | 2 | 3 | 4 | 5 | | 1 | 2 | 3 | 4 | 5 |
| 3 | 4 | 5 | 6 | 7 | | 3 | 4 | 5 | 6 | 7 |
| 4 | 5 | 6 | 7 | 8 | | 4 | 5 | 6 | 7 | 8 |
T2 T2
|[a]| b | c | d | e | f | |[a]| b | c | d | e | f |
|---+---+---+---+---+---| |---+---+---+---+---+---|
| 0 | 1 | 2 | 3 | 4 | f | | 0 | 1 | 2 | 3 | 4 | f |
| 1 | 2 | 3 | 4 |-3 | f | | 1 | 2 | 3 | 4 |-3 | t |
| 2 | 3 | 4 | 5 | 6 | f | | 2 | 3 | 4 | 5 | 6 | f |
| 3 | 4 | 5 |-5 | 7 | f | | 3 | 4 | 5 |-5 | 7 | t |
| 4 | 5 | 6 | 7 | 8 | f | | 4 | 5 | 6 | 7 | 8 | f |
T3 T3
|[a]| b | c | d | e | |[a]| b | c | d | e |
|---+---+---+---+---| |---+---+---+---+---|
| 1 |nul|nul|nul|-3 |
| 3 |nul|nul|-5 |nul|

Answer 2

that solution is fine for five columns. How about 100 columns. You need dynamic T-SQL.
The below code is quite long and divided into 4 sections.
Section 1 - Create the database, test tables, and test data.
Section 2 - My user defined function for a delimited column list and Jeff Moden's split function.
Section 3 - Dynamic T-SQL, assumes first column is key and last column is flag. Uses EXCEPT command to find row differences.
Section 4 - Dynamic T-SQL, compares column 2 in T1 to column 2 in T2 with case statement. Continued for all columns. Insert into T3 for only rows that have a difference.
-- THIS CODE WILL WORK FOR A DYNAMIC LIST OF COLUMNS, NOT JUST 4! --
-- 1 - Create test tables w/data
-- the master db
use master;
go
-- create test database
create database test;
go
-- use test
use test;
go
-- create table 1
if (OBJECT_ID('t1') <> 0) drop table t1;
go
create table t1
( key1 int, col1 int, col2 int, col3 varchar(16), col4 varchar(16) );
go
-- create table 2
if (OBJECT_ID('t2') <> 0) drop table t2;
go
create table t2
( key1 int, col1 int, col2 int, col3 varchar(16), col4 varchar(16), flag1 int default 0);
go
-- create table 3
if (OBJECT_ID('t3') <> 0) drop table t3;
go
create table t3
( key1 int, col1 int, col2 int, col3 varchar(16), col4 varchar(16) );
go
-- Add 5 rows to t1
insert into t1 values (1, 2, 4, 'A', 'B');
insert into t1 values (2, 4, 8, 'C', 'D');
insert into t1 values (3, 6, 12, 'E', 'F');
insert into t1 values (4, 8, 16, 'G', 'H');
insert into t1 values (5, 10, 20, 'I', 'J');
select * from t1;
-- Add 5 rows to t2
insert into t2 (key1, col1, col2, col3, col4) values (1, 2, 4, 'A', 'B');
insert into t2 (key1, col1, col2, col3, col4) values (2, 4, 8, 'C', 'D');
insert into t2 (key1, col1, col2, col3, col4) values (3, 6, 12, 'E', 'F');
insert into t2 (key1, col1, col2, col3, col4) values (4, 8, 16, 'G', 'H');
insert into t2 (key1, col1, col2, col3, col4) values (5, 10, 20, 'I', 'K');
select * from t2;
--
-- 2A - Declare helper function for column name list
--
-- use test
use test;
go
-- remove function if it exists
if (OBJECT_ID('dbo.get_column_list') <> 0)
drop function get_column_list;
go
-- create new function
create function get_column_list (#schema_name sysname, #table_name sysname, #del_value varchar(10) = ',') returns varchar(max)
as
begin
-- nothing to do
if (#table_name is null) return null;
-- misc variables
declare #list varchar(max) = '';
-- select the changed items
select
#list += c.name + #del_value
from
sys.schemas s join sys.objects o on s.schema_id = o.schema_id
join sys.columns c on o.object_id = c.object_id
where
o.type = 'u' and
s.name = #schema_name and
o.name = #table_name
order by c.column_id;
-- remove last delimiter
select #list = substring(#list, 1, len(#list) - len(#del_value));
-- return a list
return #list
end;
go
--
-- 2B - spliter function from jeff moden
--
-- http://www.sqlservercentral.com/articles/Tally+Table/72993/
-- You download and install as TVF in [TEST] database
--
-- 3 - Find row differences using except
--
-- declare/initialize variables
declare #stmt1 varchar(max) = '';
-- column lists
declare #list1 varchar(max) = dbo.get_column_list ('dbo', 't1', ', ');
declare #list2 varchar(max) = dbo.get_column_list ('dbo', 't2', ', ');
-- key (first), flag (last)
declare #key1 sysname = left(#list1, charindex(',', #list1, 1) - 1);
declare #key2 sysname = reverse(left(reverse(#list2), charindex(',', reverse(#list2), 1) - 2));
-- make dynamic sql
select #stmt1 = '(select ' + #list1 + ' from t2 except select ' + #list1 + ' from t1) as d1';
select #stmt1 = 'update t2 set ' + #key2 + ' = 1 where ' + #key1 + ' in (select d1.' + #key1 + ' from ' + #stmt1 + ');';
-- debug line
--print #stmt1;
-- execute the sql
exec (#stmt1);
go
--
-- 4 - Find the columns differences using case
--
-- declare/initialize variables
declare #stmt varchar(max) = '';
-- column list
declare #list varchar(max) = dbo.get_column_list ('dbo', 't2', ',');
-- key (first), flag (last)
declare #key1 sysname = left(#list, charindex(',', #list, 1) - 1);
declare #key2 sysname = reverse(left(reverse(#list), charindex(',', reverse(#list), 1) - 1));
-- select the changed items (skip key & flag)
select
#stmt += 'case when s.' + Item + ' = t.' + Item + ' then null else t.' + Item + ' end as val_' + Item + ', '
from
DelimitedSplit8K (#list, ',')
where
ItemNumber not in
(
select min(ItemNumber) as skip_vals from DelimitedSplit8K (#list, ',')
union
select max(ItemNumber) as skip_vals from DelimitedSplit8K (#list, ',')
);
-- complete the statement
select #stmt = 'insert into t3 select t.' + #key1 + ',' + substring(#stmt, 1, len(#stmt) - 1) + ' from t1 as s join t2 as t on s.' + #key1 + ' = t.' + #key1 + ' where t.' + #key2 + ' = 1 ';
-- debug line
--print #stmt;
-- execute the sql
exec (#stmt);
go