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DB2 Articles
Page 11 of 13
How to create a DB2 segmented tablespace TABSPAC2 in storage group STOGRP1?
A segmented table space is divided in multiple segments. A segment is defined as a contiguous set of fixed number of pages. This fixed number is defined during the table space definition using the SEGSIZE parameter. The SEGSIZE serves multiple purposes - It defines the tablespace as segmented and also defines the size of the segment.In a segmented tablespace, the rows of a table are stored in one or more segments and a particular segment can only have rows from one table.The segmented tablespace can be created by using the CREATE TABLESPACE command with SEQSIZE parameter as below.CREATE TABLESPACE TABSPA1 ...
Read MoreHow to add a row compression to a DB2 table TAB1?
A compression is used to save the DB2 disk space. The compression can be used either at row level or at a page level. In order to add a row compression in a DB2 table, we can give the following command−ALTER TABLE DBSET1.TAB1 COMPRESS YES STATICWe have to use ALTER TABLE for the compression of the DB2 table. The ALTER TABLE reserved words are followed by the name of DB2 table qualified by database. COMPRESS YES STATIC will complete the row compression for the said table.
Read MoreHow to delete a DB2 table TAB1?
We can delete the unused tables in the DB2. However, we must keep in mind that if we delete a table then all the indexes associated with the table are also dropped. Moreover, the triggers and views for the deleted table will become inaccessible. To delete any table in DB2, we can issue below command.DROP TABLE DBSET1.TAB1The DROP TABLE reserved word will be followed by the name of the table qualified by the database. The mentioned table will be deleted from the DB2 permanently.
Read MoreHow to change the length of the Name column from CHAR(20) to CHAR(50)?
DB2 gives us an option of modifying the attribute of the existing column in a table. We have to use the ALTER COLUMN parameter with ALTER TABLE as below in order to achieve this.ALTER TABLE DBSET1.TAB1 ALTER COLUMN NAME SET DATATYPE CHAR(50);The ALTER TABLE reserved words are followed by the name of the table qualified by a database, which is DBSET1.TAB1 in this case. Similarly, ALTER COLUMN is followed by the name of the column which needs to be modified, which NAME (of the student) in this case.In the SET DATATYPE parameter, we can pass the ...
Read MoreHow to create a table TAB2 having same attributes & columns as for table TAB1
DB2 gives us an option to copy the structure of an existing table to a new table. To copy the attributes and column of table TAB1 to a new table TAB2 we can use the following command−CREATE TABLE DBSET1.TAB2 LIKE DBSET1.TAB1The CREATE TABLE reserved words are followed by table name. The table name needs to be qualified by a database in which it will reside. In this case this new table is TAB2 and its database is DBSET1.The LIKE parameter is used after that followed by the name of the original table qualified by its database i.e. DBSET1.TAB1The important ...
Read MoreHow to create a view on table TAB1 for column Name, age, enrollmentId & age > 10 years. >
A view is an alternative way of representing the data stored in a table. A view can be used to increase the performance of the query since the view contains very limited rows as compared to its source table. We can use the below command to create a view on an existing table TAB1.CREATE VIEW AGEVIEW (NAME, AGE, ENROLLMENT_ID) AS SELECT NAME, AGE, ENROLLMENT_ID FROM TAB1 WHERE AGE > 10;We have to use CREATE VIEW reserved words in order to create a new view. This will be followed by the name of the view (AGEVIEW).The columns ...
Read MoreForeign key referencing of two DB2 tables
A foreign key is a column in a table that establishes a referential link with another table. A foreign key can be defined during creation of table (CREATE TABLE command) or it can be defined by modifying the table (ALTER TABLE command). However, before defining any key as foreign key, make sure that an index is built up on that column. We can use the below command to define an existing column CLASS in table TAB1 as a foriegn key which links to table TAB2.ALTER TABLE TAB1 ADD FOREIGN KEY (CLASS) REFERENCES CLASSDATA (CLASS_ID);The ALTER TABLE reserved words are followed ...
Read MoreHow to add a new column Address in the above DB2 table TAB1?
We can add a new column in an existing table as per the business requirements. Similarly, we can also remove a column from the table. This could be done using the ALTER table command as below.ALTER TABLE TAB1 ADD COLUMN ADDRESS VARCHAR(100);The ALTER TABLE reserved words are followed by the name of the table which we want to amend. In this case it is TAB1.To add a new column we will use ADD COLUMN and to remove the column we will use the REMOVE COLUMN parameter. This is followed by the name of the column. If this is an addition ...
Read MoreHow will you add a constraint on above DB2 table TAB1 for ages between 3 to 16 years?
Constraints are used to restrict the data inserted at a particular column. Constraints can be used in such a way that a value can only be inserted if it satisfies the condition given in constraints. We can give the below parameter during CREATE TABLE command to add a constraint.CREATE TABLE DBSET1.TAB1 (STUDENT_ID CHAR(10) NOT NULL, ENROLLMENT_ID CHAR(20) NOT NULL, NAME VARCHAR(50), AGE SMALLINT CONSTRAINT NUMBER CHECK (AGE >=3 AND AGE
Read MoreHow to add a unique index on the above table TAB1 for column Enrollment ID (ascending)?
An index is a lookup table that optimizes the searching of data. An index defined on any table can increase the query speed. The index can be built up on any column of the table and DB2 will generate a logical structure at backend. This will facilitate the search on the table using indexed columns effectively.An index can be unique and non-unique. To create a new unique index at any table we can use below command.CREATE UNIQUE INDEX ENROTAB1 ON TAB1 (ENROLLMENT_ID) ASC;The CREATE UNIQUE INDEX reserved words are followed by the name of the unique index which we ...
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