I use basic sql querying for my day to day work, but I regularly find myself needing to run queries in different tables using the same where clauses.
What I would ideally like to do is locally set a value to a name, for example:
traderef = ABCD1234. It's kind of like Defining a name in excel.
and then use 'traderef' in my queries,
select * from table1 where tranid = traderef
select * from table2 where tranid = traderef and otherattr = 'xyz1'
I only have query access to the dbs that i use, i have tried to google results, and found some info re SET
TIA
Declare a bind variable using the SQL/Plus and SQL Developer command VARIABLE name data_type and assign it a value using EXECUTE (or a PL/SQL anonymous block) and then use it in your queries:
VARIABLE traderef VARCHAR2(20)
EXEC :traderef := 'ABCD1234';
SELECT * FROM table1 WHERE tranid = :traderef;
SELECT * FROM table2 HWERE tranid = :traderef AND otherattr = 'xyz1';
Related
I have table which has basically 2 rows containing the name of failure and the main table i want to write a query such that
Select main
from xyz
will return the table name like abc.
Now I want to get the data from the abc table
Select *
from
(select main
from xyz)
which returns abc.
How can I write it ?
You must use dynamic sql.
Note, that you can't use "SELECT to nowhere" in a compound statement in Db2. That is, the following code is erroneous.
BEGIN
SELECT * FROM MYTAB;
END#
This is why you need to store the result of SELECT somewhere. You may use Global Temporary Tables for that presuming, that USER TEMPORARY TABLESPASE is available to use for your user.
--#SET TERMINATOR #
BEGIN
DECLARE V_STMT VARCHAR (500);
SELECT
'DECLARE GLOBAL TEMPORARY TABLE SESSION.RESULT'
|| ' AS (SELECT * FROM '
|| MAIN
|| ') WITH DATA WITH REPLACE '
|| 'ON COMMIT PRESERVE ROWS NOT LOOGED'
INTO V_STMT
FROM XYZ
-- place your WHERE clause here if needed
FETCH FIRST 1 ROW ONLY
;
EXECUTE IMMEDIATE V_STMT;
END
#
SELECT * FROM SESSION.RESULT
#
dbfiddle link.
Here is a solution on stack that shows how to get the table names from your database
DB2 Query to retrieve all table names for a given schema
Then you could take your failure table and join into it based off of the table name, that should match your errors to the table that match on the table name. I'm not a 100% sure of your question but I think this is what you are asking.
The inner system query has schema and name. Type is T for table. See IBM link below for column reference. You could run the query wide open in the inner query to look for the tables you want. I would recommend using schema to isolate your search.
https://www.ibm.com/docs/en/db2-for-zos/11?topic=tables-systables
SELECT
ft.*
, st.*
FROM [FailureTable] as ft
INNER JOIN
(
select * from sysibm.systables
where CREATOR = 'SCHEMA'
and name like '%CUR%'
and type = 'T'
) st
ON st.[name] = ft.[tablename]
You can try
DECLARE #tableName VARCHAR(50);
SELECT #tableName = main
FROM xyx
EXEC('SELECT * FROM ' + 'dbo.' + #tableName)
Dont forget to add validation if #tableName doesnt get populated
I'm using DBVisualiser to run the following script (Expecting to pass variable in query and retrieve data based on where condition)
set Id='1';
select * from MyTable where account_id = '${hivevar:Id}' limit 5
Unfortunatelly, when I run this script I see that query which is executed is as follows:
set Id='1';
select * from mytable where account_id = '${hivevar:Id}' limit 5
But when I run query with hardcoded value
select * from mytable where account_id = '1' limit 5
then I get expected dataset.
I would apprecaie if anyone could help me to learn what I do wrong.
Thanks in advance.
Variables which were set without namespace are hiveconf variables, not hivevar. Though you can specify the namespace explicitly.
Try this:
set Id=1; --No need to quote here if it is quoted in the select
-- use hiveconf
select * from MyTable where account_id = '${hiveconf:Id}' limit 5;
Or this:
--specify the namespace
set hivevar:Id=1;
select * from MyTable where account_id = '${hivevar:Id}' limit 5;
See also similar question.
Environment: Db2 for i, version 7.3
Library/table structure:
CORPORATE/TENANTS
LIB01/INVOICE
LIB02/INVOICE
LIB03/INVOICE
…
LIBxx/INVOICE
The CORPORATE/TENANTS table contains a list of libraries where information about each tenant is stored. It has this structure and data:
CREATE OR REPLACE TABLE TENANTS (
ID BIGINT GENERATED ALWAYS AS IDENTITY (START WITH 1),
TENANT CHAR(10) NOT NULL,
PRIMARY KEY(ID)
) RCDFMT TENANTSR;
RUNSQLSTM SRCFILE(HILLB/QDDLSRC) SRCMBR(TENANTS) DFTRDBCOL(CORPORATE)
+--+------+
|ID|TENANT|
+--+------+
| 1|LIB01 |
| 2|LIB02 |
|..|......|
|99|LIB99 |
+--+------+
The LIBxx/INVOICE tables are all identical to each other and have this structure:
CREATE OR REPLACE TABLE INVOICE (
ID BIGINT GENERATED ALWAYS AS IDENTITY (START WITH 1),
PAYDAT INTEGER(6,0) NOT NULL,
AMOUNT DECIMAL(15,2) NOT NULL DEFAULT 0,
PRIMARY KEY(ID)
) RCDFMT INVOICER;
+--+------+------+
|ID|PAYDAT|AMOUNT|
+--+------+------+
| 1|180701|100.00|
| 2|180801| 35.00|
|..|......|......|
+--+------+------+
I want to generate a list of invoice amounts for all tenants for a given date:
180701 LIB01 100.00
180701 LIB02 140.00
180701 LIB03 74.00
…
Conceptually what I want to do is this (yes, I know this is invalid SQL):
SELECT PAYDAT, TENANT, AMOUNT
FROM $X.INVOICE
WHERE PAYDAT = 180701;
I want to pull data from the INVOICE table for each TENANT but I know the FROM clause cannot be dynamic like this. I’m sure this kind of query has a name but I don’t know what it is so I’m unable to effectively use a search engine to find what I need.
This would be trivial to solve with an RPGLE program but I need a pure SQL solution.
Please note - the LIBxx values CANNOT be hardcoded in any way. These values can change at any time.
To do what you want, you can use a stored procedure with an EXECUTE IMMEDIATE in a loop to build a result set. Something like this:
Note: this is not a complete cut and paste solution, but you can modify it to do what you want.
CREATE OR REPLACE PROCEDURE GETINVOICEAMOUNTS ( )
DYNAMIC RESULT SETS 1
LANGUAGE SQL
NOT DETERMINISTIC
MODIFIES SQL DATA
CALLED ON NULL INPUT
SET OPTION COMMIT = *NONE
BEGIN
DECLARE STMT VARCHAR(1024);
DECLARE RECORD_FOUND INTEGER DEFAULT 1;
DECLARE LIBRARY CHAR(10);
DECLARE C1 CURSOR FOR
SELECT TENANT FROM CORPORATE/TENANT;
DECLARE C2 CURSOR WITH RETURN FOR
SELECT * FROM SESSION.TMP ;
DECLARE CONTINUE HANDLER FOR NOT FOUND
SET RECORD_FOUND = 0;
DECLARE GLOBAL TEMPORARY TABLE TMP
(PAYDAT INTEGER(6,0),
TENANT CHAR(10),
AMOUNT DECIMAL(15,2))
WITH REPLACE;
OPEN C1;
LOOP
FETCH C1 INTO LIBRARY;
IF RECORD_FOUND = 0;
LEAVE LOOP;
END IF;
SET STMT = 'INSERT INTO SESSION.TMP SELECT PAYDAT, LIBRARY, AMOUNT FROM ' || RTRIM(LIBRARY) || '.INVOICE WHERE PAYDAT = 180701';
EXECUTE IMMEDIATE STMT
END LOOP;
CLOSE C1;
OPEN C2;
END;
I gave you more than I planned to. But, one specific modification you will invariably need is to parameterize the date that you want to retrieve.
This is how it works:
A global temporary table named TMP is used to collect the records to be returned in a result set. Once all the records are collected, a cursor is opened over TMP and the procedure ends. This causes the values collected in TMP to be returned as a result set.
To collect the values the CORPORATE/TENANT file is read, and the column TENANT is retrieved into the variable LIBRARY. For each record a statement is built that concatenates LIBRARY into an INSERT statement. This statement is executed which loads the record into TMP. I am using EXECUTE IMMEDIATE because I cannot use a parameter marker to replace the table reference in the INSERT statement, so a prepared statement is just extra work.
You could use UNION ALL:
SELECT sub.PAYDAT, t.TENANT, sub.AMOUNT
FROM (SELECT * FROM LIB01.INVOICE
UNION ALL
SELECT * FROM LIB02/INVOICE
...
SELECT * FROM LIB0n/INVOICE) sub
JOIN TENANTS t
ON sub.id = t.id
WHERE SUB.PAYDAT = 180701;
It is an SELECT * FROM sales + #yymm template.
EDIT:
More secure way is to create a view:
CREATE VIEW combined_invoice
AS
SELECT * FROM LIB01.INVOICE
UNION ALL
SELECT * FROM LIB02/INVOICE
...
SELECT * FROM LIB0n/INVOICE;
And query:
SELECT sub.PAYDAT, t.TENANT, sub.AMOUNT
FROM combined_invoice sub
JOIN TENANTS t
ON sub.id = t.id
WHERE SUB.PAYDAT = 180701;
Of course view should be altered after adding/removing tables.
I'm working on a e-learning project in which there is a table named chapter in which there is a column named question_table this is table in which the specific chapter's questions are added.
Now the problem is I want to display all the question from all the chapter for this I used following sql query
SELECT * FROM (SELECT `question_table` FROM `chapter`)
but it doesn't work and gives the error:
"Every derived table must have its own alias".
Note: I want to do it using SQL not PHP.
Firstly, I think you would be better redesigning your database. Multiple tables of the same structure holding the same data are generally not a good idea.
However what you require is possible using a MySQL procedure to build up some dynamic SQL and then execute it, returning the resulting data.
A procedure as follows could be used to do this:-
DROP PROCEDURE IF EXISTS dynamic;
delimiter //
CREATE PROCEDURE dynamic()
BEGIN
DECLARE question_table_value VARCHAR(25);
DECLARE b INT DEFAULT 0;
DECLARE c TEXT DEFAULT '';
DECLARE cur1 CURSOR FOR SELECT `question_table` FROM `chapter`;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET b = 1;
OPEN cur1;
SET b = 0;
WHILE b = 0 DO
FETCH cur1 INTO question_table_value;
IF b = 0 THEN
IF c = '' THEN
SET c = CONCAT('SELECT * FROM `',question_table_value, '`');
ELSE
SET c = CONCAT(c, ' UNION SELECT * FROM `',question_table_value, '`');
END IF;
END IF;
END WHILE;
CLOSE cur1;
SET #stmt1 := c;
PREPARE stmt FROM #stmt1;
EXECUTE stmt;
END
This is creating a procedure called dynamic. This takes no parameters. It sets up a cursor to read the question_table column values from the chapter table. It looks around the results from that, building up a string which contains the SQL, which is a SELECT from each table with the results UNIONed together. This is then PREPAREd and executed. The procedure will return the result set from the SQL executed by default.
You can call this to return the results using:-
CALL dynamic()
Down side is that this isn't going to give nice results if there are no rows to return and they are not that easy to maintain or debug with the normal tools developers have. Added to which very few people have any real stored procedure skills to maintain it in future.
In MySQL you must give every subquery ("derived table") an alias:
SELECT * FROM (SELECT question_table FROM chapter) t --notice the alias "t"
The derived table here is the result of the (SELECT ...). You need to give it an alias, like so:
SELECT * FROM (SELECT question_table FROM chapter) X;
Edit, re dynamic tables
If you know all the tables in advance, you can union them, i.e.:
SELECT * FROM
(
SELECT Col1, Col2, ...
FROM Chapter1
UNION
SELECT Col1, Col2, ...
FROM Chapter2
UNION
...
) X;
SqlFiddle here
To do this solution generically, you'll need to use dynamic sql to achieve your goal.
In general however, this is indicative of a smell in your table design - your chapter data should really be in one table, and e.g. classified by the chapter id.
If you do need to shard data for scale or performance reasons, the typical mechanism for doing this is to span multiple databases, not tables in the same database. MySql can handle large numbers of rows per table, and performance won't be an issue if the table is indexed appropriately.
I'm trying to alter a stored procedure in our DB from a hard-coded select from 1 specific DB to be able to select from any of our DB's based on an id that's passed into the sproc. Here's the stub of what the sproc is doing for us:
ALTER PROCEDURE [dbo].[GetByAdId]
(
#AdId int,
#UserCompanyId int
)
AS
SET NOCOUNT ON
SELECT
[User].[UserId],
UserMappings.IsActive,
IsAccountOwner = ( SELECT Count(*) FROM DB1_SetUp.dbo.ad Adv WHERE Adv.AdID = UserMappings.AdID AND Adv.PrimaryAccountOwnerID = [User].[UserId] )
FROM
[User] INNER JOIN UserMappings ON
(
UserMappings.UserID = [User].UserID
AND UserMappings.AdID = #AdId
AND UserMappings.UserCompanyId = #UserCompanyId
)
Basically the "IsAccountOwner" variable is hardcoded to select from DB1_SetUp every time, but we have a number of SetUp db's for different groups, so like DB2_SetUp, DB3_SetUp, etc. The UserCompanyId variable being passed into the sproc functions like a group Id and can be used to point to the particular SetUp DB I want it to select from, but I'm not sure how to do this. I basically wanted something on the ilk of:
SELECT * FROM (
CASE #UserCompanyId
WHEN 3 THEN 'DB3_SetUp'
WHEN 4 THEN 'DB4_SetUp'
)
Is there a clean way to do this, or will I have to setup this sproc on each group DB and call the specific one over on each DB?
I've done this in the past by dynamically building the SQL I wanted to execute (based on parameters passed in) and then executing the SQL using sp_executesql
see: http://msdn.microsoft.com/en-us/library/ms188001.aspx