IBM DB2 to PostgreSQL Migration

SQLines tools can help you transfer data, convert database schema (DDL), views, stored procedures, functions, triggers, queries and SQL scripts from IBM DB2 to PostgreSQL:

SQLines Data - Data transfer, schema migration and validation tool
SQLines SQL Converter - SQL scripts conversion tool

Databases:

IBM DB2 for LUW, z/OS and iSeries 11.x, 10.x, 9.x, 8.x and 7.x
PostgreSQL 16.x, 15.x, 14.x, 13.x, 12.x, 11.x, 10.x and 9.x

Migration Reference

Language Elements

Converting SQL language elements:

	DB2		PostgreSQL
1	string1 CONCAT string 2 CONCAT …	String concatenation operator	string1 \|\| string 2 \|\| …

Data Types

Data type mapping between DB2 and PostgreSQL:

	DB2		PostgreSQL
1	BIGINT	64-bit integer	BIGINT
2	BLOB(n)	Binary large object, 1 ⇐ n ⇐ 2G	BYTEA
3	CHAR(n), CHARACTER(n)	Fixed-length string, 1 ⇐ n ⇐ 254	CHAR(n), CHARACTER(n)
4	CHAR(n) FOR BIT DATA	Fixed-length byte string, 1 ⇐ n ⇐ 254	BYTEA
5	CHARACTER VARYING(n)	Variable-length string, 1 ⇐ n ⇐ 32672	VARCHAR(n)
6	CLOB(n)	Character large object, 1 ⇐ n ⇐ 2G	TEXT
7	DATE	Date (year, month and day)	DATE
8	DBCLOB(n)	UTF-16 character large object, 1 ⇐ n ⇐ 1G	TEXT
9	DECIMAL(p,s), DEC(p,s)	Fixed-point number	DECIMAL(p,s), DEC(p,s)
10	DECFLOAT(16 \| 34)	IEEE floating-point number	FLOAT
11	DOUBLE [PRECISION]	Double-precision floating-point number	DOUBLE PRECISION
12	FLOAT(p)	Double-precision floating-point number	DOUBLE PRECISION
13	GRAPHIC(n)	Fixed-length UTF-16 string, 1 ⇐ n ⇐ 127	CHAR(n)
14	INTEGER, INT	32-bit integer	INTEGER, INT
15	NCHAR(n)	Fixed-length UTF-16 string, 1 ⇐ n ⇐ 127	CHAR(n)
16	NCHAR VARYING(n)	Varying-length UTF-16 string, 1 ⇐ n ⇐ 16336	VARCHAR(n)
17	NCLOB(n)	UTF-16 character large object, 1 ⇐ n ⇐ 1G	TEXT
18	NUMERIC(p,s), NUM(p,s)	Fixed-point number	NUMERIC(p,s)
19	NVARCHAR(n)	Varying-length UTF-16 string, 1 ⇐ n ⇐ 16336	VARCHAR(n)
20	REAL	Single-precision floating-point number	REAL
21	SMALLINT	16-bit integer	SMALLINT
22	TIME	Time (hour, minute, and second)	TIME(0)
23	TIMESTAMP(p)	Date and time with fraction	TIMESTAMP(p)
24	VARCHAR(n)	Variable-length string, 1 ⇐ n ⇐ 32672	VARCHAR(n)
25	VARCHAR(n) FOR BIT DATA	Variable-length byte string, 1 ⇐ n ⇐ 32672	BYTEA
26	VARGRAPHIC(n)	Variable-length UTF-16 string, 1 ⇐ n ⇐ 16336	VARCHAR(n)
27	XML	XML data	XML

Built-in SQL Functions

Converting string functions:

	DB2		PostgreSQL
1	LOCATE(substring, string)	Get position of substring in string	POSITION(substring IN string)
2	VARCHAR(exp, length)	Convert to string	CAST(exp AS VARCHAR(length))
2	VARCHAR(exp)	Convert to string	CAST(exp AS VARCHAR)

Converting date and time functions:

	DB2		PostgreSQL
1	DATE(exp)	Convert to date (year, month and day)	DATE(exp)	Not documented
2	DAY(exp)	Extract day	EXTRACT(DAY FROM exp)
3	MONTH(exp)	Extract month	EXTRACT(MONTH FROM exp)
4	TIMESTAMP(exp)	Convert to timestamp (date and time)	CAST(exp AS TIMESTAMP)
5	YEAR(exp)	Extract year	EXTRACT(YEAR FROM exp)

SELECT Statement

Converting SQL queries:

	DB2		PostgreSQL
1	SELECT … MINUS SELECT …	Exclude rows returned by 2nd query	SELECT … EXCEPT SELECT …

CREATE TABLE Statement

Converting CREATE TABLE statement:

	DB2		PostgreSQL
1	FOR COLUMN system_name	System column name (OS/400)	Removed
2	FOR BIT DATA	Binary data encoding	Removed
2	FOR SBCS \| MIXED DATA	Column data encoding (z/OS)	Removed
3	CCSID ASCII \| UNICODE \| EBCDIC	Character set	Removed
3	CCSID num	Column character set (OS/400)	Removed

Implicit DEFAULT values in DB2:

	DB2	PostgreSQL
1	column CHAR(n) WITH DEFAULT	column CHAR(n) DEFAULT ''
2	column VARCHAR(n) WITH DEFAULT	column VARCHAR(n) DEFAULT ''
3	column INTEGER WITH DEFAULT	column INTEGER DEFAULT 0
4	column DECIMAL(p, s) WITH DEFAULT	column DECIMAL(p, s) DEFAULT 0
5	column NUMERIC(p, s) WITH DEFAULT	column NUMERIC(p, s) DEFAULT 0
6	column DATE WITH DEFAULT	column DATE DEFAULT CURRENT_DATE
7	column TIMESTAMP WITH DEFAULT	column TIMESTAMP DEFAULT NOW()
8	column CLOB WITH DEFAULT	column TEXT DEFAULT ''

CREATE INDEX Statement

Converting CREATE INDEX statement keywords and clauses:

	DB2	PostgreSQL
1	CREATE INDEX schema.index_name	CREATE INDEX index_name	Can contain index name only

CREATE PROCEDURE Statement

Converting CREATE PROCEDURE statement from IBM DB2 to PostgreSQL:

	DB2	PostgreSQL
1	CREATE OR REPLACE PROCEDURE name	CREATE OR REPLACE PROCEDURE name
2	(IN \| OUT \| INOUT param datatype(length), …)	(IN \| OUT \| INOUT param datatype(length), …)
3	LANGUAGE SQL	Removed
4	BEGIN procedure_body END	AS $$ BEGIN procedure_body END; $$ LANGUAGE plpgsql;

For more information, see Conversion of Procedural SQL Statements.

Procedural SQL Statements

Converting procedural SQL statements used in stored procedures, functions and triggers from IBM DB2 to PostgreSQL:

Variable declarations:

	DB2		PostgreSQL
1	Declarations are inside BEGIN END block		Declarations are before BEGIN END block
2	DECLARE var datatype DEFAULT value		var datatype DEFAULT value
3	DECLARE var, var2, … datatype		var datatype; var2 datatype; …
4	DECLARE cur CURSOR FOR query	Cursor declaration	cur CURSOR FOR query
5	DECLARE GLOBAL TEMPORARY TABLE	Create a temporary table	CREATE TEMPORARY TABLE

Variable Assignments:

	DB2	PostgreSQL
1	SET v1 = value	v1 := value
2	SET v1 = value, v2 = value2, …	v1 := value; v2 := value2; …
3	SET (v1, v2, …) = (value, value2, …)	v1 := value; v2 := value2; …
4	SET (v1, v2, …) = (SELECT c1, c2, …)	SELECT c1, c2, … INTO v1, v2, …
5	VALUES c1, c2, … INTO v1, v2, …	v1 := c1; v2 := c2; …

Cursor operations:

	DB2		PostgreSQL
1	DECLARE cur CURSOR FOR query	Cursor declaration	cur CURSOR FOR query
2	DECLARE cur CURSOR WITH RETURN ...	Return result set	OUT cur REFCURSOR
3	DECLARE cur WITH RETURN FOR stmt PREPARE stmt FROM 'query_string'	Dynamic cursors	OPEN cur FOR EXECUTE 'query_string'

Executing stored procedures:

	DB2		PostgreSQL
1	CALL proc_name	Execute a stored procedure	CALL proc_name

SQL Statements

Converting SQL statements:

	DB2		PostgreSQL
1	VALUES	Return one or more rows	SELECT ... UNION ALL SELECT ...

SQLines SQL Converter

SQLines Data

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Database Reference