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Problem: What is INTEGRITY in a DB2? Explain DOMAIN, ENTITY and REFERENTIAL integrity with the help of an example in ORDERS table.SolutionThe integrity refers to the accuracy, consistency and correctness of data present in the DB2 database. Data integrity is imposed during the database design to make sure that data residing in the database remains complete, accurate and reliable.There are three types of integrity described in below figure.Domain integrityIt ensures that column data in the DB2 table adhere to the permissible set of values. For example, in the ORDERS table, the domain integrity on the ORDER_DATE column ensures that data ... Read More
The duplicate INVOICE_ID in ORDERS DB2 table can be found by using a combination of GROUP BY with HAVING clause and COUNT function. The GROUP BY will enable us to group the result invoice wise and COUNT function will enable us to count the number of occurrences in each group. We can use predicate in HAVING clause to filter the results for groups having count greater than one.Below is the SQL query which we can use to find duplicate invoices in ORDERS DB2 table.ExampleSELECT INVOICE_ID FROM ORDERS GROUP BY INVOICE_ID HAVING COUNT(INVOICE_ID) > 1For example, if we have ... Read More
Problem: Write a query on TRANSACTIONS DB2 table to list down the number of orders (ORDER_ID) assigned to a particular transaction (TRANSACTION_ID).SolutionWe can use the below query to find out the number of orders assigned to a particular transaction id on TRANSACTIONS DB2 table.ExampleSELECT TRANSACTION_ID, COUNT(ORDER_ID) FROM TRANSACTIONS GROUP BY TRANSACTION_IDWe will use GROUP BY function on the ORDER_ID to fetch the result order wise. The COUNT function will count the number of orders. For example, we have below DB2 ORDERS table.TRANSACTION_IDORDER_IDIRN22345A23118IRN22345A45901IRN22345A67990IRN56902A23119IRN99781A67921IRN56902A23167 The result of our DB2 query will return the below result.TRANSACTION_IDCOUNT(ORDER_ID)IRN223453IRN569022IRN997811Read More
When we get -551 in the SQLCODE then there is some privilege level issue. It signifies that the user does not have access to the database/tablespace/view/table that he is trying to access. As per the IBM documentation -551 SQLCODE states that.Example-551 auth-id DOES NOT HAVE THE PRIVILEGE TO PERFORM OPERATION operation ON OBJECT object-nameThere are DCL (Data control language) statements which are used by DBAs in order to control the access on DB2 objects. We can raise a request with DBA to provide access to the particular object for which user is getting -551 SQLCODE.Following DCL statement will give access ... Read More
Both QMF and SPUFI are tools built to access DB2 databases in a mainframe environment. Using these tools, we can SELECT, UPDATE and DELETE the data from the DB2 database. QMF stands for Query Management Facility and SPUFI stands for SQL Processor Using File Input.Below are the differences between QMF and SPUFI.SPUFI is a free tool which comes with mainframe DB2 installation, while QMF is a separate licensed toolQMF is an interactive tool which can be used for reporting and formatting purposes, but in case of SPUFI, we need to write the SQL queries in the mainframe dataset and the ... Read More
The OPTIMIZE FOR N ROWS is a DB2 clause which we can add in the query to give priority for the retrieval of the first few rows only. This clause will enable the optimizer to choose the access path that minimizes the response time for fetching first few rows.The OPTIMIZE FOR N ROWS clause is not effective on SELECT DISTINCT and COUNT function because DB2 will need the entire qualifying rows in order to fetch the DISTINCT rows or COUNT the number of rows. The OPTIMIZE FOR N ROWS clause gives DB2 a better opportunity to establish the access path.The ... Read More
The TRIGGERS are the event driven database programs which are triggered automatically by the database. The TRIGGERS are created using the CREATE TRIGGER statement.For example, we want to create a TRIGGER which will update ORDER_COMMISION column of the ORDERS table to 5% of the ORDER_TOTAL value after every new record insertion in ORDERS table.ExampleCREATE TRIGGER ORDERCOMMUPD AFTER INSERT ON ORDERS FOR EACH ROW MODE DB2SQL BEGIN ATOMIC UPDATE ORDERS SET ORDER_COMMISION=(5*ORDER_TOTAL)/100;Using the above statement, we have created an AFTER trigger which will be triggered automatically after any new row is inserted in the ORDERS table. Similarly, we can have BEFORE ... Read More
The TRIGGERS are database programs which are triggered automatically by DBMS in response to any modification done on the specified table. A TRIGGER can be associated with only a single table and they cannot be skipped if the desired event occurs.The TRIGGERS are like STORED PROCEDURES in the sense, both are pieces of code which are directly managed by DB2. However, TRIGGERS are event driven and executed automatically once the desired event occurs (INSERT/UPDATE/DELETE) on the specified table.The STORED PROCEDURES on the other hand needs to be called explicitly in the application program. Another difference between them is, TRIGGERS are ... Read More
A STORED PROCEDURE generally contains the SQLs which are often used in one or more programs. The main advantage of STORED PROCEDURE is that it reduces the data traffic between the COBOL and DB2 as the STORED PROCEDURES resides in DB2.A COBOL-DB2 program can call a STORED PROCEDURE using a CALL statement and we can have nested STORED PROCEDURE upto 16 levels. For example, if we have STORED PROCEDURE with a name ORDERSTAT, then we can call it in our COBOL-DB2 program using the below command:ExampleEXEC SQL CALL ORDERSTAT (:WS-ORDER-ID, :WS-ORDER-STATUS) END-EXECIn order to create a DB2 procedure, we ... Read More
Problem: What will be the result if a COBOL-DB2 program tries to query a DB2 table, but the database in which table is residing is down?SolutionWhen we try to access any table using a COBOL-DB2 program and the DB2 database in which that table is residing is down then the COBOL-DB2 program will abend. In this case, the SQLCODE of SQLCA field will have the value as -904.As per the IBM documentation SQLCODE -904 states.“Unavailable resource. The database or tablespace is not available for use”There are several methods which we can use in order to find the current status of ... Read More