This may sound stupid, but I would like to know if there is a way to verify if a list of tables exists before doing an action. If I have 12 tables to verify, do I have to repeat “If exists bla bla bla” 12 times?
I tried doing …
IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = ’employee_id’
and TABLE_NAME = N’employee_address’
and TABLE_NAME = N’employee_division’ )
But it not working. Any idea?
Your statement will never be true, because table name cannot be one of the these AND at the same time be another of them. In such scenario you can use OR instead of AND, but this will check does at least one of these tables exists. You must either combine 12 EXISTS statements with the names of the tables with AND conditions, or select the count of rows where table name is in list, i.e.:
IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'employee_id')
and EXISTS(SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = N'employee_address'
and EXISTS(SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = N'employee_division' )
or
IF ((SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME in ('employee_id', N'employee_address', N'employee_division' )) = 3)
Related
I have an AWS database with multiple tables that I am trying to get the row counts for in a single query.
The ideal query output would be:
table_name row_count
table2_name row_count
etc...
So far I've been able to either get all the table names from the database or all the rowcounts of the tables (in random order), but not both in the same query.
This query returns a column of all the table names that exist in the database:
SELECT table_name FROM information_schema.tables WHERE table_schema = '<database_name>';
This query returns all the row counts for the tables:
SELECT COUNT(*) FROM table_name
UNION ALL
SELECT COUNT(*) FROM table2_name
UNION ALL
etc..for the rest of the tables
The issue with this query is that is displays the row counts in a random order that doesn't correspond with the order of the tables in the query, and so I don't know which row count goes with which table - hence why I need both the table names and row counts.
Simply add the names of the tables as literals in your queries:
SELECT 'table_name' AS table_name, COUNT(*) AS row_count FROM table_name
UNION ALL
SELECT 'table_name2' AS table_name, COUNT(*) AS row_count FROM table_name2
UNION ALL
…
The following query generates the UNION query to produce counts of all records.
The problem to solve is that (as of December 2022) INFORMATION_SCHEMA.TABLES incorrectly defines every table and view as a BASE TABLE so you will need some logic to eliminate the views.
In Data Warehousing it is common practise to record snapshots of the record counts of landing tables at frequent intervals. Any unexpected deviations from expected counts can be used for reporting/alerting
WITH Table_List AS (
SELECT table_schema,table_name, CONCAT('SELECT CURRENT_DATE AS run_date, ''',table_name, ''' AS table_name, COUNT(*) AS Records FROM "',table_schema,'"."', table_name, '"') AS BaseSQL
FROM INFORMATION_SCHEMA.TABLES
WHERE
table_schema = 'YOUR_DB_NAME' -- Change this
AND table_name LIKE 'YOUR TABLE PATTERN%' -- Change or remove this line
)
, Total_Records AS (
SELECT COUNT(*) AS Table_Count
FROM Table_List
)
SELECT
CASE WHEN ROW_NUMBER() OVER (ORDER BY table_name) = Table_Count
THEN BaseSQL
ELSE CONCAT(BaseSql, ' UNION ALL') END AS All_Table_Record_count_SQL
FROM Table_List CROSS JOIN Total_Records
ORDER BY table_name;
SELECT *
FROM information_schema.__internal_partitions__
WHERE table_schema = 's1'
AND table_name = 't1'
ORDER BY partition_numberenter code here
Can we get partition details for all the tables at the same time using the above query ? Like where table_schema IN (s1,s2) AND table_name IN (t1,t2)
I got this statement, which works in Oracle:
update table a set
a.attribute =
(select
round(sum(r.attribute1),4)
from table2 p, table3 r
where 1 = 1
and some joins
)
where 1 = 1
and a.attribute3 > 10
;
Now I would like to do the same statement in Exasol DB. But I got error [Code: 0, SQL State: 0A000] Feature not supported: this kind of correlated subselect (Session: 1665921074538906818)
After some research, I found out you need to write the query in following syntax:
UPDATE table a
set a.attribute = r.attribute2
FROM table a, table2 p, table3 r
where 1 = 1
and some joins
and a.attribute3 > 10;
The problem is I can't take sum of r.attribute2. So I get unstable set of rows. Is there any way to do the first query in Exasol DB?
Thanks for help guys!
Following SQL UPDATE statement will work for cases if JOIN between table1 and table2 are 1-to-1 (or if there is a 1-to-1 relation between target table and resultset of JOINs)
In this case target table val column is updated otherwise an error is returned
UPDATE table1 AS a
SET a.val = table2.val
FROM table1, table2
WHERE table1.id = table2.id;
On the other hand, if the join is causing multiple returns for single table1 rows, then the unstable error raised.
If you want to sum the column values of the multiplying rows, maybe following approach can help
First sum all rows of table2 in bases of table1 and use this sub-select as a new temp table, then use this in UPDATE FROM statement
UPDATE table1 AS a
SET a.val = table2.val
FROM table1
INNER JOIN (
select id, sum(val) val from table2 group by id
) table2
ON table1.id = table2.id;
I tried to solve the issue using two tables
In your case probably you will use table2 and table3 in the subselect statement
I hope this is the answer you were looking for
I have 2 tables. table1 and table2
Table1 is pointing to s3://bucket/Dicrectory1/year/month/day/hour/file (25 records) and
Table2 is pointing to s3://bucket/Dicrectory2/year/month/day/hour/file (2 records)
My query looks like below
SELECT table1.column1,
table2.column1
FROM table1
LEFT JOIN table2
ON table1.column1 = table2.column1
WHERE table1.year = '2018'
AND table1.month = '10'
AND table1.day = '31'
AND table1.hour = '00'
and table2.year = '2018'
AND table2.month = '10'
AND table2.day = '31'
AND table2.hour = '00'
Even though I am doing left join I am only getting inner join results (2 Records common in both tables).
Am I not doing the left join correctly for Athena?
If there is no corresponding record in table2, all table2.* will be null and this gets thrown away by the where clause. (answer stolen from Left Outer Join Not Working? )
I'm doing a count from table1 whose records/rows don't exist in table2
Here is the query:
select count(1) from table1
where not exists (select 1 from table2 where
table1.col1 = table2.col1
and table2.id=1)
I need to see the records that are missing in table2 , whose id in table2=1, and these records should be available in table1. The PK here is col1.
The query returns me 0. But if I do an excel sheet comparing by removing both the tables to excel. I can find 1591 records that are missing from table1 and are available in table2.
Your query is working fine.
You query finds records that EXISTS in table1 but not in table2
You have found with excel records that does NOT EXISTS in table1 and EXISTS in table2
If you'd like to find these records with SQL than your query should be:
select count(1) from table2
where table2.id=1 and table2.col1 not in (select col1 from table1)
or with not exists version of this query:
select count(1) from table2
where table2.id=1 and
not exists (select 1 from table1 where table1.col1=table2.col1)
I didn't test the queries.