SQL – DDL
Data Definition Language
Copyright  1992, 1993 BY DMC CONSULTING, INC.
ALL RIGHTS RESERVED
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AS/400 is a trademark of International Business Machines Corporation
SQL/400
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SQL – DDL – Creating Schemas
SQL/400
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Objectives
Upon completion of this segment, you will
have a thorough understanding of:
•
•
•
•
Collections and Schemas
Creating Schemas
Schema Contents
Schema Commands
You will also perform the following task:
• Create a schema
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What is a Schema
Simply put, a schema (also called collection) is a group of
tables. These tables are logically linked together for easier
management. On the System i, schemas are implemented as
Libraries within the DB2 database. Not just a library though, but
also all of the management objects within the schema that are
used by the SQL engine to manage the schema.
Knowing what these objects are and how to use them is very
practical knowledge.
Schemas contain the following objects by default:
SQL/400
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What is a Schema
Catalog
SYSTABLES
SYSCOLUMNS
SYSINDEXES
SYSKEYS
SYSVIEWS
SYSVIEWDEP
SYSPACKAGE
SYSCHKCST
SYSCST
SYSCSTCOL
SYSCSTDEP
SYSKEYCST
SYSREFCST
SYSTRIGCOL
SYSTRIGDEP
SYSTRIGGER
SYSTRIGUPD
Syntax:
CREATE SCHEMA schema-name
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Journals
QSQJRN
QSQJRN0001
What is a Schema
SET CURRENT SCHEMA schema-name
This statement sets the default schema for created objects
as well as the default schema for objects referenced in
other SQL statements, but not procedures and functions.
Correctly specifying the current schema can greatly
simplify SQL syntax by removing the location to find
SQL/400
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What is a Schema
SET OPTION DFTRDBCOL = schema-name
When creating procedures and functions, its possible to
define the default database schema (collection) using the
SET OPTION statement as shown below:
CREATE PROCEDURE procedure-name
LANGUAGE SQL
SET OPTION DFTRDBCOL = schema-name
BEGIN
procedure-code;
END
SQL/400
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What is a Schema
SET PATH = “schema-name”, schema-name, schema-name,…
The SQL path is used to resolve unqualified references to
User Defined Functions , User Defined Data Types, and
Stored Procedures. The default behavior of SQLPATH
changes based upon the naming convention in use:
*SYS Naming, SQLPATH = “*LIBL”
*SQL Naming, SQLPATH = “QSYS,QSYS2,user-id”
To best use this feature, create a procedure in each environment
(test,production, etc) Define that procedure shown below,
replacing the schema name with the data schema for that
environment.
SQL/400
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What is a Schema
CREATE PROCEDURE Set_Schema
LANGUAGE SQL
BEGIN
SET CURRENT SCHEMA schema-name
END
In any other stored procedure, call the Set_Schema
procedure at the beginning of the code to correctly set
the data schema being used in this environment. It
should avoid the need for hard coded schema names.
CREATE PROCEDURE Other_Proc
LANGUAGE SQL
BEGIN
CALL Set_Schema;
…
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SQL Create Statement
Tables
The CREATE statement allows the user to build a
new table. All of the fields (columns) must
also be defined. Their data type, length, and
null attributes must be described. And
optional constraints may be defined as well.
There are three different version of the CREATE
TABLE statement:
1) CREATE TABLE table-name (definition)
2) CREATE TABLE LIKE other-table
3) CREATE TABLE AS (select-statement)
SQL/400
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SQL Create Statement
CREATE TABLE table-name (definition)
CREATE TABLE lib/table
(field1 datatype(length) null,
field2 datatype(length) null,
field3 datatype(length) null,
etc......, constraint1, constraint2,
etc.........)
The library/schema name is optional. For compatibility with RPG IV,
the file and field names should not exceed
10 characters. For RPG/400, field names cannot
exceed 6 characters.
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SQL Create Statement
Data Types
CHAR – Up to 32,767 bytes of alphanumeric data (32.765 if Null capable)
DECIMAL – Up to 63 digits of packed numeric data
NUMERIC – Up to 63 digits of zoned numeric data.
DATE – Date Data type using a 4 digit year
TIME – Time data type in 24 hr format
TIMESTAMP - Timestamp data type include date, time, and microseconds (6 digits)
INTEGER (INT) – Large Integer (4 Bytes)
SMALLINT – A small integer (2 Bytes)
BIGINT – A big integer (8 Bytes)
FLOAT – Floating Point data type (8 Bytes)
VARCHAR - Up to 32,740 bytes of character data (32.739 if Null capable)
LONG VARCHAR – Variable Length Character Data up to the length of the row
BINARY – Up to 32,767 bytes of binary data (32,765 if Null Capable)
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SQL Create Statement
Data Types
VARBINARY - Up to 32,740 bytes of binary data (32.739 if Null capable)
GRAPHIC – Up to 16,383 double byte characters (16,382 if Null capable)
VARGRAPHIC – Up tp 16370 double byte characters (16,369 if Null capable)
LONG VARGRAPHIC – A string of double byte characters up to the length of the row
DOUBLE – Double precision floating point (8 Bytes)
REAL – Single Precision Floating point (4 Bytes)
BLOB – Variable length binary string up to 2 gigabytes in length
CLOB – Variable length string of characters up to 1 gigabyte in length
DATALINK – A string up to 32,718 bytes containing a URL (32,717 if Null capable)
DBCLOB – Variable length double byte character string up to 1 gigabyte in length
User-Defined (UDT) – Custom functions built with the CREATE FUNCTION statement
ROWID - System generated key that uniquely defines a row (40 Bytes)
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SQL Create Statement
When defining fields their null attribute can be:
Omitted: To allow null values
NOT NULL: To prevent null values from being loaded into a field
NOT NULL WITH DEFAULT: To use default values in place of null
values
CREATE TABLE MYTEST
(PART CHAR(10) NOT NULL WITH DEFAULT,
OQTY NUMERIC(5, 0) NOT NULL,
COST NUMERIC(7, 2) NOT NULL WITH DEFAULT 19.99,
DESC CHAR(20))
SQL/400
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SQL Create
Statement
Constraints
Primary key: A set of fields which must contain unique,
non-null values.
Unique key: A set of fields which must contain unique
values.
Foreign key: A set of fields which must match the key
to the parent file.
Check: A set of fields whose values must meet a
defined criteria.
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SQL Create
Statement
Constraints
CONSTRAINT name type (values)
CONSTRAINT CUST_KEY PRIMARY KEY (FIELDA)
CONSTRAINT VALID_CUST FOREIGN KEY (CUSTNO)
REFERENCES CUST (CNUMBER) ON DELETE
CASCADE ON UPDATE NO ACTION
CONSTRAINT FIELDC_VALIDITY CHECK (FIELDC <> 0 )
CONSTRAINT VALID_ORDER UNIQUE (ORDER#)
SQL/400
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SQL Create Statement
CREATE TABLE LIKE other-table
CREATE TABLE MYTABLE LIKE YOURTABLE
INCLUDING IDENTITY
or
CREATE TABLE MYTABLE LIKE YOURTABLE
EXCLUDING IDENTITY
SQL/400
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SQL Create Statement
CREATE TABLE AS (Select-Statement)
CREATE TABLE MYTABLE AS
(SELECT * FROM YOURTABLE)
WITH DATA
CREATE TABLE MYTABLE AS
(SELECT * FROM YOURTABLE)
WITH NO DATA
CREATE TABLE MYTABLE AS
(SELECT KEYFLD, SUM(QTYFLD) AS TOTAL
FROM YOURTABLE GROUP GROUP BY KEYFLD)
WITH DATA
SQL/400
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SQL Create Statement
Identity Columns
What is an Identity Column?
An identity column is a column in an SQL table which is partially
under system control, and is used to create a unique key to a
database. These must defined at the time of the table creation,
though they can altered after the fact, but not added.
An Identity column must be defined as Decimal, Numeric, Integer,
Smallint, or Bigint. It has a starting and ending value as well as an
increment. If the CYCLE option is used, then when the ending
value is reached, the next new record uses the starting value.
Essentially “wrapping” the identity value.
SQL/400
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SQL Create Statement
Identity Columns
These columns are ideal as keys to a database table. Using an identity
column in place of a meaningful data item such as Part Number, Employee
Number, or Order Number enables us to freely change those values and treat
them as easily maintained data columns.
PartID Part# Description
1
A101 Widget
2
A102 Sprocket
3
C100 Cog
SQL/400
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Price
19.99
19.99
19.99
SQL Create Statement
Identity Columns
CREATE TABLE PARTMAST
(PARTKEY DECIMAL (6,0) NOT NULL
GENERATED ALWAYS AS IDENTITY
(START WITH 100001
INCREMENT BY 1
CYCLE
CACHE 100
NO ORDER),
PARTDESC AS CHAR(30))
SQL/400
03/03/2003
DMC Consulting, 1993
SQL Create Statement
Identity Columns
CREATE TABLE PARTMAST
(PARTKEY DECIMAL (6,0) NOT NULL
GENERATED BY DEFAULT AS IDENTITY
(START with 100001
INCREMENT BY 1
MINVALUE 100001
MAXVALUE 900000
NO CYCLE
NO CACHE
ORDER),
PARTDESC AS CHAR(30))
SQL/400
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SQL Create Statement
Identity Columns
GENERATED ALWAYS – System assigns value, no value can be
specified for this field on INSERT statements
GENERATED BY DEFAULT – System assigns value if no value was
specified for this field on INSERT statements
START WITH x – Beginning value for inserted rows
INCREMENT BY x – Amount added to value for each row
CYCLE – After reaching the MAXVALUE restart at MINVALUE
NO CYCLE – No restart after reaching MAXVALUE
(until alter table xxxxx alter column yyyyy restart is run)
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SQL Create Statement
CACHE x – Allocate x identity values in memory for faster INSERTS (must be 2
or more)
NO CACHE – Do not preallocate identity values
ORDER – Identity values must be issued in order
NO ORDER – Identity values may be issued in any order
IDENTITY_VAL_LOCAL() – Function returns the last Identity value issued at
“same level”. This means within the same function or procedure. Do not use
in a before trigger.
INSERT INTO PARTMAST (PARTDESC) VALUES(‘NEW PART’)
INSERT INTO PARTHIST SELECT * FROM PARTMAST WHERE PARTID
= IDENTITY_VAL_LOCAL()
*See ROWID for information OVERRIDING options on Insert
SQL/400
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SQL Create Statement
Row ID Columns
What is a ROWID Column?
ROWIDs are similar to identity columns in that they uniquely
identify rows within the database. Unlike an identity column,
ROWID is a datatype with a 40 byte length. Either the system
will assign the ROWID, or one can be assigned by the user.
But in the later case it must be a valid row-id generated by the
database.
CREATE TABLE PARTMAST
(PARTKEY ROWID GENERATED ALWAYS,
PARTDESC AS CHAR(30))
SQL/400
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SQL Create Statement
Row ID Columns
The ROWID() Function can be used to translate a character string back
into a row id data type. This presumes the character string was created
by casting a valid row id value into a character string with the CAST
function.
When inserting data into a table with either a ROW ID or an Identity
Column the following clauses may precede the values clause.
SQL/400
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SQL Create Statement
Row ID Columns
OVERRIDING USER VALUE – This tells the SQL Engine to ignore row id
or identity column values given on an insert, and that the system
should generate appropriate values instead.
OVERRIDING SYSTEM VALUE – This tells the SQL Engine to recognize
row id or identity column values given on an insert, and that the system
should not generate these values.
INSERT INTO PARTMAST
OVERRIDING USER VALUE
VALUES(0,’New Part’)
SQL/400
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SQL Create Statement
Table Creation Scripts
It is useful to have an easy executed and modified script/program
available to delete and recreate tables, indexes and views.
Because the SQL Engine has certain predictable patterns when
searching for an optimal index, controlling the sequence they are
created in, can improve performance. Text members executed with
RUNSQLSTM can be used for this purpose.
CREATE TABLE PARTMAST
(PARTID DECIMAL (6,0) GENERATED BY DEFAULT AS IDENTITY
(START WITH 100001 MINVALUE 100001 MAXVALUE 100010
INCREMENT BY 1 NO CYCLE NO CACHE NO ORDER),
PARTDESC CHAR(30));
RUNSQLSTM SRCFILE(lib/file) SRCMBR(mbr)
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SQL Create Statement
Table Creation Scripts
Besides using RUNSQLSTM, other options such as these may be
used:
This task can be performed by QMQRY script files.
An SQL script file executed via iSeries Navigator
A High Level Language program with embedded SQL
A stored procedure.
SQL/400
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SQL Create Statement
CREATE PROCEDURE PARTMAST_BUILD
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
CREATE TABLE PARTMAST
(PARTID DECIMAL (6,0) GENERATED BY DEFAULT AS
IDENTITY (START WITH 100001 MINVALUE 100001
MAXVALUE 100010
INCREMENT BY 1 NO CYCLE NO CACHE NO ORDER),
PARTDESC CHAR(30));
CALL PARTMAST_ADD_INDEX;
END
SQL/400
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SQL Create Statement
A complete set of procedures may be used to manage a table
and all its related objects.
CREATE PROCEDURE PARTMAST_ADD_INDEX
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
ALTER TABLE PARTMAST ADD CONSTRAINT
PARTMAST_PRI_KEY
PRIMARY KEY (PARTID);
CREATE UNIQUE INDEX PARTMAST_UNIQUE_DESC ON
PARTMAST(PARTDESC);
END
SQL/400
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SQL Create Statement
CREATE PROCEDURE PARTMAST_DROP
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
CALL PARTMAST_DROP_INDEX;
DROP TABLE PARTMAST;
END
CREATE PROCEDURE PARTMAST_DROP_INDEX
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
ALTER TABLE PARTMAST DROP CONSTRAINT
PARTMAST_PRI_KEY;
DROP INDEX PARTMAST_UNIQUE_DESC;
END
SQL/400
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SQL Create Statement
CREATE PROCEDURE PARTMAST_REINDEX
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
CALL PARTMAST_DROP_INDEX;
CALL PARTMAST_ADD_INDEX;
END
SQL/400
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SQL Create Statement
Materialized Query
CREATE TABLE INVTOTALS AS
(WITH TEMP AS (SELECT DEC(SUM(IQTY),7,0) as TOTAL,
IITEM FROM INVDET
GROUP BY IITEM)
SELECT MITEM,MDESC, MITMPRC, MITMCST, TOTAL
FROM ITMMST LEFT JOIN TEMP ON MITEM = IITEM)
DATA INITIALLY DEFERRED
REFRESH DEFERRED
ENABLE QUERY OPTIMIZATION
MAINTAINED BY USER
See IBM’s White paper for more details at
http://www-03.ibm.com/servers/enable/site/education/wp/438a/438a.pdf
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SQL Create Statement
DATA INITIALLY DEFERRED indicates that the MQT is not loaded with
data at the time of creation. Use DATA INITIALLY IMMEDIATE to load it
with data right away if necessary
REFRESH DEFERRED indicates that the user may choose to refresh
the table at any time by issuing the REFRESH TABLE mqt-name
statement. This clause is not optional.
ENABLE QUERY OPTIMIZATION indicates that the SQL engine may
choose to use this MQT to satisfy other SQL statements issued against
the underlying table(s). To deactivate this feature, use DISBALE QUERY
OPTIMIZATION instead.
MAINTAINED BY USER indicates that the user is responsible for
loading the correct data into the MQT using INSERT, UPDATE, DELETE,
and REFRESH TABLE statements. This is not optional.
SQL/400
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SQL Create Statement
Managing Materialized Queries
The data within an MQT is static, meaning that once data is loaded into
it, it will not change regardless of what happens to the underlying
tables. Programmers may choose to manually update the MQT with
INSERT, UPDATE, and DELETE statements, or more likely, they can
repopulate the table with current data using the REFRESH TABLE
statement such as the one shown below.
REFRESH TABLE INVTOTALS
QAQQINI File
To enable the use of MQTs within the SQL optimizer, the QAQQINI
file must be updated, as the default settings do not allow the use
of Materialized Queries during the optimization process. These
settings are needed:
MATERIALIZED_QUERY_TABLE_USAGE = *ALL
MATERIALIZED_QUERY_TABLE_REFRESH_AGE = *ANY
SQL/400
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SQL Create Statement
Global Temporary Table
DECLARE GLOBAL TEMPORARY TABLE
ORDER_BATCH
(ORDER DECIMAL(5,0),
CUSTOMER DECIMAL (7,0),
DUEDATE DATE,
STATUS CHAR(1))
DECLARE GLOBAL TEMPORARY TABLE
ORDER_BATCH
AS (SELECT ORDER, CUSTOMER, DUEDATE DATE,
STATUS FROM ORDMAST WHERE BATCHNO = 12345)
WITH DATA
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SQL Create Statement
Global Temporary Table
DECLARE GLOBAL TEMPORARY TABLE ORDER_BATCH
LIKE ORDMAST
SELECT * FROM SESSION/ORDER_BATCH
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Triggers and
Constraints
SQL/400
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Check Constraints
RPG
Program
Check
Constraint
Database
File
The Check constraint enforces basic edit rules such as:
•PLTNO <> 0
•STATUS <> “ “
•YNFLD = “Y” OR YNFLD = “N”
•SHIFT > 0 AND SHIFT < 4
•DAYOFWEEK(WEDT) = 1
SQL/400
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Check Constraints
ALTER TABLE PARTMAST
ADD CONSTRAINT
PARTMAST_PRICE_NOT_ZERO CHECK (PRICE > 0)
ALTER TABLE ORDMAST
ADD CONSTRAINT
ORDMAST_VALID_STATUS CHECK
(STATUS = ‘A’ OR STATUS = ‘P’ OR STATUS = ‘C’)
ALTER TABLE PARTMAST
ADD CONSTRAINT
PARTMAST_VALID_DATA CHECK
(TYPE = ‘L’ AND PRICE = 0 OR TYPE <> ‘L’)
SQL/400
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Primary/Unique Key Constraints
Child File
- Primary Key
Pugsley Adams
Wed.
Adams
Bobby Brady
Cindy Brady
Greg
Brady
Jan
Brady
Marsha Brady
ALTER TABLE PARTMAST ADD CONSTRAINT
PARTMAST_PRI_KEY PRIMARY KEY (PARTID)
SQL/400
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Primary/Unique Key Constraints
Child File
-Unique Key
Pugsley Adams
Wed.
Adams
null
Brady
null
Brady
Greg
Brady
Jan
Brady
Marsha Brady
ALTER TABLE PARTMAST ADD CONSTRAINT
PARTMAST_UNIQUE_DESC UNIQUE KEY (PARTDESC)
SQL/400
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Referential Constraints
Child File
Pugsley
Wed.
Bobby
Cindy
Greg
Jan
Marsha
SQL/400
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Adams
Adams
Brady
Brady
Brady
Brady
Brady
RPG
Program
Referential
Constraint
Parent File
Adams
Brady
Cleaver
Munster
Referential Constraints
ALTER TABLE INVDETAIL
ADD CONSTRAINT “VALID PART” FOREIGN KEY (PARTID)
REFERENCES PASRTMAST (PARTID) ON DELETE
CASCADE ON UPDATE NO ACTION
ON UPDATE… No Action – Do not allow parents records with dependents to have their parent key
column(s) changed.. (Journalling required)
Restrict - Do not allow parents records with dependents to have their parent key
column(s) changed. (Journalling not required)
ON DELETE… No Action – Do not allow parents records with dependents to be deleted.
(Journalling required)
Restrict - Do not allow parents records with dependents to be deleted.
(Journalling not required)
Cascade - If a parent record is deleted, cascade the delete to the dependent file,
and delete all records associated with that parent record.
Set Default - If a parent record is deleted, Set the key fields in the dependent file to
their default values for all records associated with that parent record.
Set Null- If a parent record is deleted, Set the key fields in the dependent file to
null for all records associated with that parent record.
SQL/400
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Indexes and Views
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SQL/400
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SQL Create Statement
Index
CREATE {UNIQUE} INDEX lib/index-name
ON lib/table-name (field1 {ASC/DESC}, field2 {ASC/DESC}, field3
{ASC/DESC}...)
CREATE UNIQUE INDEX CUSTNAME
ON CUST (CNAME)
CREATE INDEX CUSTCITY
ON CUST (CSTATE, CCITY)
CREATE INDEX INVAVAIL
ON INVDET (IITEM, IQTY DESC)
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SQL Create Statement
Encoded Vector Index
CREATE ENCODED VECTOR INDEX lib/index ON lib/table (field1
{ASC/DESC}, field2 {ASC/DESC}, field3 {ASC/DESC}...) WITH n DISTINCT
VALUES;
CREATE ENCODED VECTOR INDEX USER001/CUSTST ON CUST USER001/CUST
(CSTATE) WITH 60 DISTINCT VALUES;
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SQL Create Statement
Views
CREATE VIEW view-name AS
SELECT field1, field2, field3, etc...
FROM base-table
WHERE condition
SQL/400
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SQL Create Statement
Summary Views
ORDER
1
1
1
1
1
1
DATE
LOC
QTY
01/15/1999
01/16/1999
01/17/1999
01/20/1999
01/21/1999
A10
A10
A10
A10
A10
100
100
100
100
100
500
CREATE VIEW view-name (column1, column2, etc...) AS
SELECT column1, Sum(column2), AVG(column3), etc...
FROM base-table
GROUP BY column1
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SQL Create Statement
Alias
Alias
A
A
Alias
D
B
C
D
E
MULTI-MEMBER TABLE
CREATE ALIAS PARTMAST_MBR_A FOR PARTMAST (A)
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Triggers
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Trigger Programs
Data Base
Changes
Trigger
Program
Data
Base
Triggers can be written in SQL or as external programs in languages such as
RPGLE.
If the trigger program needs to abort the update, end it by sending an
escape message with a severity of 50 or higher.
Up to 300 Triggers can be associated with a single file.
iSeries Navigator provides a wizard to assist in creating triggers.
SQL/400
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Triggers
CREATE TRIGGER your-lib.CUST_TRIGGER AFTER INSERT ON KPFLIB.CUST
REFERENCING NEW TABLE AS N
FOR EACH STATEMENT MODE DB2SQL
BEGIN
insert into your-lib.custhist (cnumber,cname)
select n.cnumber,n.cname from n;
END;
SQL/400
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Triggers
New/Old: Referencing New Row as xxx - for insert
Referencing Old Row as yyy – for delete
Referencing New Row as xxx
Old Row as yyy – for update
(use Row syntax with DB2SQL or DB2ROW modes)
Referencing New Table as xxx - for insert
Referencing Old Table as yyy – for delete
Referencing New Table as xxx
Old Table as yyy – for update
(use Table syntax with DB2SQL mode and not BEFORE triggers)
SQL/400
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Triggers
CREATE TRIGGER your-lib.CUST_TRIGGER AFTER INSERT ON KPFLIB.CUST
REFERENCING NEW ROW AS N
FOR EACH ROW MODE DB2ROW
BEGIN
insert into your-lib.custhist (cnumber,cname)
values(n.cnumber,n.cname);
END;
SQL/400
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Triggers
For Each: Use FOR Each ROW to force the trigger to run for each row
affected.
Use FOR EACH STATEMENT to force the trigger to run once
for each SQL statement that might trigger it. This trigger will
run even if no rows are affected.
Mode:
DB2ROW fires the trigger as each row is affected, and
allows access to individual rows only.
DB2SQL fires after all the statement is complete, and allows
access to either rows or tables.
SQL/400
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Triggers
CREATE TRIGGER Load_Candidates
INSTEAD OF INSERT ON ORDERS
REFERENCING NEW AS NEW_ROW
FOR EACH ROW
MODE DB2SQL
INSERT INTO CANDIDATES VALUES(NEW_ROW.A1,NEW_ROW.A2)
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DMC Consulting, 1993
Summary
•Schemas
•Table Creation
•Scripts
•Materialized Queries
•Global Temporary Tables
•Indexes
•Views
•Constraints
•Triggers
SQL/400
03/03/2003
DMC Consulting, 1993