There are 4 table in a DB as A, B, C and D. That tables has exact same structure.
I need to use same set of procedures to process those table and generate a single file
several utility procedures are available in my design i need to pass a row as a parameter for those procedure.
What is best way to implement a PLSQL script for that purpose ?
Please provide a high level overview?
Note:
my basic problem is use a common cursor and a common rowtype for this.
Oracle Native Dynamic SQL it's an easy way to query any table using fixed set of parameters and result variables (including records):
EXECUTE IMMEDIATE 'select ... from ' || table_name || ' where ....'
USING in_par_1, in_par2, OUT out_par_1, ...;
OPEN <cursor> FOR 'select ... from ' || table_name || ' where ....'
using ...;
LOOP
FETCH <cursor> INTO ...;
EXIT WHEN <cursor>%NOTFOUND;
...
END LOOP
(and others ways to dynamic data exchange are provided).
The biggest NDS problem is the lack of compile-time error checks, so it might be not easy to support it and there is a risk to break something and don't even notice that.
In your case one good trick can be used:
create a View which aggregates all data and marks its data source
create only one procedures set which depends on common data structure (the view) and data source ID (procedure's parameter).
The sample listing:
create or replace view view_abcd as
select 'a' as data_type, a.* from a
union
select 'b', b.* from b
union
select 'c', c.* from c
union
select 'd', d.* from d;
... procedure/function process_data( dataType ) ...
select .... from view_abcd v where v.data_type = dataType and ...
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 creating an update statement that generate SHA256 for table columns based on table's name
1st Step: I created a procedure that get the table columns, concatenate it all in one columns, then format to a desired format.
-- Procedure code : Extract table's columns list, concatenate it and format it
Create procedure SHA_PREP (in inp1 nvarchar(20))
as
begin
SELECT concat(concat('hash_sha256(',STRING_AGG(A, ', ')),')') AS Names
FROM (
SELECT concat('to_varbinary(IFNULL("',concat(COLUMN_NAME,'",''0''))')) as A
FROM SYS.TABLE_COLUMNS
WHERE SCHEMA_NAME = 'SCHEMA_NAME' AND TABLE_NAME = :inp1
AND COLUMN_NAME not in ('SHA')
ORDER BY POSITION
);
end;
/* Result of this procedures :
hash_sha256(
to_varbinary("ID"),to_varbinary(IFNULL("COL1",'0')),to_varbinary(IFNULL("COL2",'0')) )
*/
-- Update Statement needed
UPDATE "SCHEMA_NAME"."TABLE_NAME"
SET "SHA" = CALL "SCHEMA_NAME"."SHA_PREP"('SCHEMA_NAME')
WHERE "ID" = 99 -- a random filter
The solution by #SonOfHarpy technically works but has several issues, namely:
unnecessary use of temporary tables
overly complicated string assignment approach
use of fixed system table schema (SYS.TABLE_COLUMNS) instead of PUBLIC synonym
wrong data type and variable name for the input parameter
An improved version of the code looks like this:
create procedure SHA_PREP (in TABLE_NAME nvarchar(256))
as
begin
declare SQL_STR nvarchar(5000);
SELECT
'UPDATE "SCHEMA_NAME"."TABLE_NAME" SET "SHA"= hash_sha256(' || STRING_AGG(A, ', ') || ')'
into SQL_STR
FROM (
SELECT
'TO_VARBINARY(IFNULL("'|| "COLUMN_NAME" ||'",''0''))' as A
FROM TABLE_COLUMNS
WHERE
"SCHEMA_NAME" = 'SCHEMA_NAME'
AND "TABLE_NAME" = :TABLE_NAME
AND "COLUMN_NAME" != 'SHA'
ORDER BY POSITION
);
-- select :sql_str from dummy; -- this is for debugging output only
EXECUTE IMMEDIATE (:SQL_STR);
end;
By changing the CONCAT functions to the shorter || (double-pipe) operator, the code becomes a lot easier to read as the formerly nested function calls are now simple chained concatenations.
By using SELECT ... INTO variable the whole nonsense with the temporary table can be avoided, again, making the code easier to understand and less prone to problems.
The input parameter name now correctly reflects its meaning and mirrors the HANA dictionary data type for TABLE_NAME (NVARCHAR(256)).
The procedure now consists of two commands (SELECT and EXECUTE IMMEDIATE) that each performs an essential task of the procedure:
Building a valid SQL update command string.
Executing the SQL command.
I removed the useless line-comments but left a debugging statement as a comment in the code, so that the SQL string can be reviewed without having to execute the command.
For that to work, obviously, the EXECUTE... line needs to be commented out and the debugging line has to be uncommented.
What's more worrying than the construction of the solution is its purpose.
It looks as if the SHA column should be used as a kind of shorthand row-data fingerprint. The UPDATE approach certainly handles this as an after-thought activity but leaves the "finger-printing" for the time when the update gets executed.
Also, it takes an essential part of the table design (that the SHA column should contain the fingerprint) away from the table definition.
An alternative to this could be a GENERATED COLUMN:
create table test (aaa int, bbb int);
alter table test add (sha varbinary (256) generated always as
hash_sha256(to_varbinary(IFNULL("AAA",'0'))
, to_varbinary(IFNULL("BBB",'0'))
)
);
insert into test (aaa, bbb) values (12, 32);
select * from test;
/*
AAA BBB SHA
12 32 B6602F58690CA41488E97CD28153671356747C951C55541B6C8D8B8493EB7143
*/
With this, the "generator" approach could be used for table definition/modification time, but all the actual data handling would be automatically done by HANA, whenever values get changed in the table.
Also, no separate calls to the procedure will ever be necessary as the fingerprints will always be current.
I find a solution that suits my need, but maybe there's other easier or more suitable approchaes :
I added the update statement to my procedure, and inserted all the generated query into a temporary table column, the excuted it using EXECUTE IMMEDIATE
Create procedure SHA_PREP (in inp1 nvarchar(20))
as
begin
/* ********************************************************** */
DECLARE SQL_STR VARCHAR(5000);
-- Create a temporary table to store a query in
create local temporary table #temp1 (QUERY varchar(5000));
-- Insert the desirable query into the QUERY column (Temp Table)
insert into #temp1(QUERY)
SELECT concat('UPDATE "SCHEMA_NAME"."TABLE_NAME" SET "SHA" =' ,concat(concat('hash_sha256(',STRING_AGG(A, ', ')),')'))
FROM (
SELECT concat('to_varbinary(IFNULL("',concat(COLUMN_NAME,'",''0''))')) as A
FROM SYS.TABLE_COLUMNS
WHERE SCHEMA_NAME = 'SCHEMA_NAME' AND TABLE_NAME = :inp1
AND COLUMN_NAME not in ('SHA')
ORDER BY POSITION
);
end;
/* QUERY : UPDATE "SCHEMA_NAME"."TABLE_NAME" SET "SHA" =
hash_sha256(to_varbinary("ID"),to_varbinary(IFNULL("COL1",'0')),to_varbinary(IFNULL("COL2",'0'))) */
SELECT QUERY into SQL_STR FROM "SCHEMA_NAME".#temp1;
--Excuting the query
EXECUTE IMMEDIATE (:SQL_STR);
-- Dropping the temporary table
DROP TABLE "SCHEMA_NAME".#temp1;
/* ********************************************************** */
end;
Any other solution or improvement are well welcomed
Thank you
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 want a program to access a table/view/stored procedure, etc. (something materialized, let's call it X) that abstracts the real location of the data contained in three basic tables (the tables have the same definition in all locations).
I would want X to fetch the server name, catalog name and table name from somewhere (a table, probably) and access the specific three basic tables. The caller of X would not know which specific tables were being called.
How can I do this in SQL Server (2008)?
Like a function, a view can't use dynamic SQL - it can't go find some metadata reference somewhere and adjust accordingly.
I think the closest thing to what you want is a synonym. Let's say you have three different databases, A, B and C. In A the table you want the view to reference is dbo.foo, in B it is dbo.bar, and in Cit is dbo.splunge. So then you could create a synonym like so in each database:
USE A;
GO
CREATE SYNONYM dbo.YourCommonViewName FOR dbo.foo;
GO
USE B;
GO
CREATE SYNONYM dbo.YourCommonViewName FOR dbo.bar;
GO
USE C;
GO
CREATE SYNONYM dbo.YourCommonViewName FOR dbo.splunge;
GO
Now this technically isn't a view, but in each database you can say...
SELECT <cols> FROM dbo.YourCommonViewName;
...and it will return the data from the database-specific table.
To do this in a stored procedure would be much simpler. Say you store the server, database and table name in some table, e.g. dbo.lookup:
CREATE TABLE dbo.lookup
(
id INT PRIMARY KEY,
[server] SYSNAME,
[database] SYSNAME,
[table] SYSNAME,
active BIT NOT NULL DEFAULT (0)
);
-- you may want a constraint or trigger to ensure
-- only one row can be active at any one time.
INSERT dbo.lookup(id, [server], [database], [table])
SELECT 1,N'serverA',N'databaseA',N'tableA'
UNION ALL SELECT 2,N'serverB',N'databaseB',N'tableB';
Now your program can say:
UPDATE dbo.lookup SET active = 1 WHERE ... ?
And your stored procedure can be:
CREATE PROCEDURE dbo.whatever
AS
BEGIN
SET NOCOUNT ON;
DECLARE #sql NVARCHAR(MAX);
SELECT #sql = N'SELECT <cols> FROM ' + QUOTENAME([server])
+ '.' + QUOTENAME([database]) + '.dbo.' + QUOTENAME([table])
FROM dbo.lookup WHERE active = 1;
EXEC sp_executesql #sql;
END
GO
I still don't understand the point, and I don't know what you're planning to do when two different users expect to call your program at the same time, and they each should get results from a different location.
Agreed with Aaron on the fact that views and functions cannot use dynamic sql.
Still what you can do is build a clr table valued function. In that you can play with .net code and query whatever you want. And build you data accordingly and output what you need.
So instead of querying the data like
select * from myview
you can query it
select * from dbo.clr_mymockupview()
Create SYNONYMs to your remote servers.
Create your VIEW to concatenate your locations together using UNION ALL.
Since you said "tables", join your tables before the UNION ALL and hopefully, MS will perform the JOIN remotely.
Use a union query with parameters for database, server, and catalog:
Select col1, col2, <etc.>, 'table1' as tablename, 'server1' as servername, 'catalog1' as catname from server1.catalog1.table1
Union Select col1, col2, <etc.>, 'table2' as tablename, 'server2' as servername, 'catalog2' as catname from server2.catalog2.table2
Union Select col1, col2, <etc.>, 'table3' as tablename, 'server3' as servername, 'catalog3' as catname from server3.catalog3.table3
Then filter based on your 3 criteria. This probably won't be blazing fast but will wonk with std. SQL.
I'm playing with some code from an article written by Peter Brawley found here on page 6 of the pdf. I'm trying to figure out how to automate it so that the result of the procedure is automatically placed in the select query. Right now what I am doing is calling the procedure, exporting the result into a text file, going to the text file manually (point click with mouse), copying the result and pasting it into a select statement. I haven't been able to figure out how to either insert the select statement into the procedure, or put the procedure into a table in my database or variable that I can call from the select statement. Any ideas?
Here is the sample code from Peter Brawley, that I've been trying to automate:
use database;
DROP PROCEDURE IF EXISTS writesumpivot;
DELIMITER |
CREATE PROCEDURE writesumpivot(
db CHAR(64), tbl CHAR(64), pivotcol CHAR(64), sumcol CHAR(64)
)
BEGIN
DECLARE datadelim CHAR(1) DEFAULT '"';
DECLARE comma CHAR(1) DEFAULT ',';
DECLARE singlequote CHAR(1) DEFAULT CHAR(39);
SET #sqlmode = (SELECT ##sql_mode);
SET ##sql_mode='';
SET #pivotstr = CONCAT( 'SELECT DISTINCT CONCAT(', singlequote,
',SUM(IF(', pivotcol, ' = ', datadelim, singlequote,
comma, pivotcol, comma, singlequote, datadelim,
comma, sumcol, ',0)) AS `',
singlequote, comma, pivotcol, comma, singlequote, '`',
singlequote, ') AS sumpivotarg FROM ', db, '.', tbl,
' WHERE ', pivotcol, ' IS NOT NULL' );
-- UNCOMMENT TO SEE THET MIDLEVEL SQL:
-- SELECT #pivotstr;
PREPARE stmt FROM #pivotstr;
EXECUTE stmt;
drop prepare stmt;
SET ##sql_mode=#sqlmode;
END
|
DELIMITER ;
call writesumpivot('database', 'table', 'pivotcol','sumcol');
Then the Select statement is as follows:
SELECT
infoField
[results of the call]
FROM
database.table
GROUP BY infoField;
Assuming I've ran the call, exported the results, copied them and pasted them into the select statement, my personal results of the call in the SELECT query would look something like this:
SELECT
infoField
,SUM(IF(pivotcol = "Yellow",sumcol,0)) AS `Yellow`
,SUM(IF(pivotcol = "Red",sumcol,0)) AS `Red`
,SUM(IF(pivotcol = "Purple",sumcol,0)) AS `Purple`
,SUM(IF(pivotcol = "Orange",sumcol,0)) AS `Orange`
,SUM(IF(pivotcol = "Green",sumcol,0)) AS `Green`
,SUM(IF(pivotcol = "Blue",sumcol,0)) AS `Blue`
,SUM(IF(pivotcol = "White",sumcol,0)) AS `White`
FROM database.table
GROUP BY infoField;
Running the above select statement gives me the pivot table that I need. I'm tryig to figure out how to incorporate this into a website, which is why it needs to be automated.
I tried inserting a create table, and then reference the table, but didn't get desired results.
Edited the last section of the PROCEDURE as follows:
--SELECT #pivotstr;
DROP TABLE IF EXISTS temp2;
CREATE TABLE IF NOT EXISTS temp2(sumpivotarg varchar(8000));
PREPARE stmt FROM #pivotstr;
...
changed call and select as follows:
call writesumpivot('database','table','pivotcol','sumcol');
insert into temp2(sumpivotarg) values(#pivotstr);
SELECT
table.infoField, temp2.sumpivotarg
FROM table, temp2
GROUP BY infoField
Results from this were the generic code rather than summing the contents of the cells in the database. it looks something like this:
infoField | sumpivotarg <-- Col Headings
123 | SELECT DISTINCT CONCAT('Sum(if(pivotcol=",pivotcol",sumcol,0)) AS'pivotcol,'')..
124 | SELECT DISTINCT CONCAT('Sum(if(pivotcol=",pivotcol",sumcol,0)) AS'pivotcol,'')..
125 | select DISTINCT CONCAT('Sum(if(pivotcol=",pivotcol",sumcol,0)) AS'pivotcol,'')..
I do not mean any disrespect towards mySQL, but this whole writing to a temp table solution for passing tablular data between stored procedures is suboptimal and dangerous (in real world transaction processing). I truly hope that the mySQL team will build in some enterprise level stored procedure functionality. Also, mySQL Functions not being able to return tables is a distinct disadvantage.
I have been slowly moving process over to Linux and mySQL from MSSQL. The short comings of mySQL in the procedure and function department is forcing some major kludgey type rewrites (ala temp tables and globals, etc).
I have been writing SPs for about 20 years (Sybase before SQL Server) and feel strongly that using dynamic SQL does not take advantage of the server side database. Many folks try to implement a Data layer at the client level, but the sever is better suited to this task. It is a natural division of functionality and data. Also, simultaneously running multiple precompiled calls at the server is quite a bit more optimal than repeated calls to the server, for the same processes.
Come on mySQL team, I am keeping my fingers crossed....
You could create a temp table in your DB. Use SQL insert to insert data into temp table as the result of the stored procedure execution. Afterwards you could use that temp table inside your select statement.
Here's an answer that shows how to do that:
Use result set of mysql stored procedure in another stored procedure
Just to mention a similar question:
MySQL How to INSERT INTO temp table FROM Stored Procedure