Data definition statements

It is recommended to avoid use of DDL in programs.

When using SQL Data Definition Language (DDL) statements such as CREATE TABLE, ALTER TABLE, DROP TABLE, only a limited SQL syntax works on all database servers. Most databases support NOT NULL, CHECK, PRIMARY KEY, UNIQUE, FOREIGN KEY constraints, but the syntax for naming constraints is different.

The following statement works with most database servers and creates a table with equivalent properties in all cases:
 CREATE TABLE customer  (
     cust_id INTEGER NOT NULL,
     cust_name CHAR(50) NOT NULL,
     cust_lastorder DATE NOT NULL,
     cust_group INTEGER,
       PRIMARY KEY (cust_id),
       UNIQUE (cust_name),
       FOREIGN KEY (cust_group) REFERENCES group (group_id)

Some engines like SQL Server have a different default behavior for NULL columns when you create a table. You may need to set up database properties to make sure that a column allows nulls if the NOT NULL constraint is not specified.

When executing CREATE TABLE or ALTER TABLE DDL statements, and Informix emulation is enabled, the ODI drivers are able to convert Informix data types like DATETIME YEAR TO MINUTE to a native SQL equivalent. This is especially required when creating temporary tables during program execution. However, the ODI drivers will not convert Informix specific table definition rules such as constraint naming.

To create tables in programs using non-standard clauses (for example to define storage options), use EXECUTE IMMEDIATE with a string containing the SQL text, and adapt the statement to the target database server.

Table 1. DDL statements by database server brand
Database Server Type Related topic
IBM® DB2® LUW See details
IBM Netezza® See details
Microsoft™ SQL Server See details
Oracle® MySQL / MariadDB See details
Oracle Database Server See details
PostgreSQL See details
SAP HANA® See details
SQLite See details