Multiple Substring Charindex - sql-server

Question

I am trying to extract strings from a column to show which are the FROM Tables and JOIN Tables. the complete string consists of one FROM Table and multiple JOIN Tables. Here is a sample of a string:
FROM [TABLEOWNER] .[load_XT_Customer_test] load_XT_Customer_test
INNER JOIN [TABLEOWNER].[load_xt_orders_test] load_xt_orders_test ON load_xt_customer_test.customer_id=load_xt_orders_test.customer_id
INNER JOIN [TABLEOWNER].[load_XT_Orders] load_XT_Orders ON
load_xt_customer_test.customer_id=load_xt_orders.customer_id
INNER JOIN [TABLEOWNER].[load_xt_order_details_test] load_xt_order_details_test
ON load_xt_customer_test.customer_id=load_xt_order_details_test.customer_id
My problem here is that there is no unique character to separate the strings, how can I dynamically extract the single join tables?
I tested it with:
SELECT st_where
,SUBSTRING(st_where
,CHARINDEX('] ',st_where,1)+1
,ABS(CHARINDEX(' ',st_where,CHARINDEX('] ',st_where,1)+1)
-CHARINDEX(']',st_where,1)-1))
AS FromTable
,SUBSTRING(st_where
,CHARINDEX('JOIN [TABLEOWNER].[',st_where,1)+19
,ABS(CHARINDEX(' ',st_where,CHARINDEX('JOIN [TABLEOWNER].[',st_where,1)+19)
-CHARINDEX('JOIN [TABLEOWNER].[',st_where,1)-20))
AS JoinTable
,SUBSTRING(st_where
,CHARINDEX('=',st_where,1)+59
,ABS(CHARINDEX(' ',st_where,CHARINDEX('=',st_where,1)+59)
-CHARINDEX('=',st_where,1)-60))
AS JoinTable2

Answer 1

This should get you started:
DECLARE #st_where nvarchar(max) =
N'
FROM [TABLEOWNER] .[load_XT_Customer_test] load_XT_Customer_test
INNER JOIN [TABLEOWNER].[load_xt_orders_test] load_xt_orders_test ON load_xt_customer_test.customer_id=load_xt_orders_test.customer_id
INNER JOIN [TABLEOWNER].[load_XT_Orders] load_XT_Orders ON
load_xt_customer_test.customer_id=load_xt_orders.customer_id
INNER JOIN [TABLEOWNER].[load_xt_order_details_test] load_xt_order_details_test
ON load_xt_customer_test.customer_id=load_xt_order_details_test.customer_id
';
SELECT
TableName =
SUBSTRING
(
SS.[value],
CharStart.pos + 1,
CharEnd.pos - CharStart.pos + 1
)
FROM STRING_SPLIT
(
-- Replace delimiter phrase with a single character
-- so we can use STRING_SPLIT
-- or use a more general string splitter
REPLACE(#st_where, N'INNER JOIN', NCHAR(256)),
NCHAR(256)
) AS SS
CROSS APPLY
(
VALUES
(
-- Find the start of the table name
CHARINDEX(N'.[', SS.[value], 1)
)
) AS CharStart (pos)
CROSS APPLY
(
VALUES
(
-- Find the end of the table name
CHARINDEX(N']', SS.[value], CharStart.pos)
)
) AS CharEnd (pos);
db<>fiddle demo
The general idea is to split the input string on the phrase "INNER JOIN" then locate the table names using ".[" and "]" as delimiters.