How do i extract texts from string and save it as two columns and add character at the end for third column - tsql

Question

I m using TSQL, I want to extract text from the string and save it as two column and third one as
The following code is not complete but just getting rid of PRD1T_ the Finapp and not sure how to cater for rest of the text
Select substring(Table_name,
charindex('_',Table_name)+1,
Len(Table_name) - charindex('.',Table_name)) as Landing_Schema_Name
FROM [e].[Load_History_test]

Answer 1

When asking questions like this it is best to provide some sample data and expected results, as Ronen suggested. For SQL questions a really good way of doing this is with a temp table and sample data, like this:
CREATE TABLE #load_history_test (
table_name VARCHAR(100)
);
INSERT INTO #load_history_test
SELECT 'PRD1T_FINAPP.HOLCONTRACT'
UNION ALL
SELECT 'PRD1T_FINAPP.TOCCASE'
UNION ALL
SELECT 'PRD1T_FINAPP.TOCCASE';
So that provides something people can run and starts towards the criteria for a minimal, reproducible example, which is the secret to getting a good answer on StackOverflow. I have used SELECT with UNION ALL as Azure Synapse does not currently support the VALUES clause for multiple records.
For expected results, it's often good to display them in a table, something like this:
col1
col2
col3
PRD1T
FINAPP
HOLCONTRACT
PRD1T
FINAPP
TOCCASE
This way it's clear to people what you expect. It is not clear why you have two TOCCASE examples in your screenprint.
For your problem, there is more than one approach. You are along the right lines with CHARINDEX, SUBSTRING and LEFT but things can start to look complicated. Therefore I tend to wrap up some complexity in a Common Table Expression (CTE), see below for an example. There is also a kind of 'trick' approach with a built-in SQL function called PARSENAME. This is designed to extract from four-part object names common in SQL Server eg <server-name>.<database-name>.<schema-name>.<object-name>. As long as your object names will never have more than four parts, this approach will work for you. See the main help for PARSENAME here. See below for a complete demo that runs end to end with a temp table to demonstrate the different principles:
IF OBJECT_ID('#load_history_test') IS NOT NULL
DROP TABLE #load_history_test;
CREATE TABLE #load_history_test (
table_name VARCHAR(100)
);
INSERT INTO #load_history_test
SELECT 'PRD1T_FINAPP.HOLCONTRACT'
UNION ALL
SELECT 'PRD1T_FINAPP.TOCCASE'
UNION ALL
SELECT 'PRD1T_FINAPP.TOCCASE';
;WITH cte AS (
SELECT
table_name AS original_table_name,
CHARINDEX( '_', table_name ) underscorePos,
CHARINDEX( '.', table_name ) stopPos,
REPLACE( table_name, '_', '.' ) AS clean_table_name
FROM #load_history_test
)
SELECT
*,
PARSENAME( clean_table_name, 3 ) a,
PARSENAME( clean_table_name, 2 ) b,
PARSENAME( clean_table_name, 1 ) c,
LEFT( original_table_name, underscorePos - 1 ) getItemBeforeUnderscore,
SUBSTRING( original_table_name, underscorePos + 1, ( ( stopPos - 1 ) - underscorePos ) ) AS getItemAfterUnderscore,
SUBSTRING( original_table_name, stopPos + 1, 99 ) getItemAfterStop
FROM cte;