Check date from all the tables in SQL Server - sql

Question

I've had like lists of 300 tables.
Every table has date column INSERT_DATE (of type Varchar).
And I wanted to check if the table is having the same date.
So that let's say - first table:
INSERT_DATE
20221231
20221231
20221231
Second table:
INSERT_DATE
20221231
20221231
20221231
Third table:
INSERT_DATE
20221230
20221230
20221230
Desired results of my query:
Table Name
Date
FIRST_TABLE
20221231
SECOND_TABLE
20221231
THIRD_TABLE
20221230
I'm confused on how to make it all "automatic" rather than querying one by one.
Like it'd take forever for me to query
SELECT TOP 1 INSERT_DATE
FROM FIRST_TABLE
then
SELECT TOP 1 INSERT_DATE
FROM SECOND_TABLE
then
SELECT TOP 1 INSERT_DATE
FROM THIRD_TABLE
Until it'd get to 300 tables.
Btw , each of the tables would have only and should have only 1 date. Because the procedure was to truncate insert, so if i saw some tables not matching the dates like the others, i knew that table have some problems and i'd have to run it manually.

Answer 1

It sounds like you need to scan the database's INFORMATION_SCHEMA to select all tables of interest and then build and execute dynamic SQL that queries each selected table and UNIONs the result.
It was unclear whether you wanted the top/max insert date or a distinct list of insert dates, so I have included SQL templates for both.
The following will select all tables having an INSERT_DATE column, and will build up and execute the necessary dynamic SQL.
-- Select tables
DECLARE #SelectedTables TABLE(TableName SYSNAME)
INSERT #SelectedTables
SELECT T.TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES T
JOIN INFORMATION_SCHEMA.COLUMNS C
ON C.TABLE_NAME = T.TABLE_NAME
AND C.TABLE_SCHEMA = T.TABLE_SCHEMA
WHERE T.TABLE_TYPE = 'BASE TABLE'
AND C.COLUMN_NAME = 'INSERT_DATE'
-- Define SQL Templates
DECLARE #SqlTemplateMax NVARCHAR(MAX) = 'SELECT TABLE_NAME = <TableNameString>, MAX(INSERT_DATE) AS INSERT_DATE FROM <TableName>
'
DECLARE #SqlTemplateDistinct NVARCHAR(MAX) = 'SELECT DISTINCT TABLE_NAME = <TableNameString>, INSERT_DATE FROM <TableName>
'
DECLARE #UnionAll NVARCHAR(10) = 'UNION ALL
'
DECLARE #OrderBy NVARCHAR(MAX) = 'ORDER BY
TABLE_NAME,
INSERT_DATE DESC
'
-- Build dynamic SQL
DECLARE #Sql NVARCHAR(MAX) = (
SELECT STRING_AGG(
REPLACE(REPLACE(#SqlTemplateDistinct
,'<TableNameString>', QUOTENAME(T.TableName, ''''))
,'<TableName>', QUOTENAME(T.TableName))
, #UnionAll)
FROM #SelectedTables T
)
SET #Sql = #Sql + #OrderBy
-- Print and Execute dynamic SQL
PRINT #Sql
EXEC (#Sql)
This will generate and execure the following dynamic SQL:
SELECT DISTINCT TABLE_NAME = 'FIRST_TABLE', INSERT_DATE FROM [FIRST_TABLE]
UNION ALL
SELECT DISTINCT TABLE_NAME = 'SECOND_TABLE', INSERT_DATE FROM [SECOND_TABLE]
UNION ALL
SELECT DISTINCT TABLE_NAME = 'THIRD_TABLE', INSERT_DATE FROM [THIRD_TABLE]
ORDER BY
TABLE_NAME,
INSERT_DATE DESC
See this db<>fiddle for a working example.
Note the use of the QUOTENAME() function above. Its use is good practice to ensure proper escaping of potential special characters when injecting 'strings' and [identifiers] into dynamic SQL.
The STRING_AGG() function joins the generated SQL fragments together, separated by the second parameter (UNION ALL in this case). If you are using an older version of SQL server that does not support STRING_AGG(), you will need to resort for using a FOR XML hack that was commonly used in the past to concatenate strings. See this db<>fiddle for the FOR XML version of the above.