PostgreSQL for MySQL Users

See also:

• PostgreSQL

Licensing:

• MySQL: Dual Licensed
• PostgreSQL: BSD-Style

Internet Resources

• Things to find out about when moving from MySQL to PostgreSQL (PostgreSQL wiki)
• PostgreSQL for MySQL Administrators (opslife blog)
• PostgreSQL for MySQL users (coderholic blog)
• Switching from MySQL to PostgreSQL - tips, tricks and gotchas? on StackOverflow

MySQL's INSERT UPDATE

Option 1) Write a function like:

 CREATE FUNCTION doinsert(_id integer, _value text) RETURNS void AS $$
 BEGIN
  UPDATE thetable SET value = _value WHERE id = _id;
  IF NOT FOUND THEN
     INSERT INTO thetable(id, value) VALUES (_id, _value);
   END IF
 END;
 $$ LANGUAGE plpgsql;

Option 2) Use two SQL statements:

 -- update the existing
 UPDATE realTable SET VALUE = (SELECT VALUE FROM tmp WHERE tmp.id = realTable.id)
 WHERE EXISTS (SELECT VALUE FROM tmp WHERE tmp.id = realTable.id);
 -- insert the missing
 INSERT INTO realTable(id, value)
 SELECT id, value FROM tmp WHERE NOT EXISTS(SELECT 1 FROM realTable WHERE tmp.id = realTable.id);

MySQL's AUTO INCREMENT

• Oracle: SEQUENCE
• MySQL: id INT UNSIGNED NOT NULL AUTO_INCREMENT
• PostgreSQL: id SERIAL oder SEQUENCE

Syntactic sugar: SERIAL

CREATE TABLE table_name (
  Identifier SERIAL,
  -- ...
);

The Explicit Way: SEQUENCE

SEQUENCE-Definition

CREATE SEQUENCE myseq;

SEQUENCE-Usage

either as the column's default value:

CREATE TABLE table_name (
  Identifier NUMBER DEFAULT nextval('myseq'),
  -- ...
);

or explicitly each time you insert a new row:

INSERT ... INTO table_name VALUES(nextval('myseq'), 'Name', ...);

• See also 1 and 2

MySQL's INT UNSIGNED (Cardinal)

• MySQL: column INT UNSIGNED
• PostgreSQL: column INT CHECK (column > 0)

MySQL's Index Type

• MySQL: INDEX idx_id(id)
• PostgreSQL: CREATE INDEX idx_id ON TABLENAME(id);

MySQL's Query Resultset Limit

• MySQL: SELECT * FROM tbl LIMIT 10, 5
• PostgreSQL: SELECT * FROM tbl LIMIT 5 OFFSET 10

Data types of MySQL versus PostgreSQL

Mysql		PostgreSQL
Typ	Beschreibung	Typ	Beschreibung
tinyint	-128..127	-	-
smallint	-32768..+32767	int2	-32767 ... +32768
int	-2147483648.. +2147483647	int4	-2147483648 ... +2147483647
		int8	+/- 18 Dezimalstellen
float(n)	n E {4;8}, Einf./doppelte Genauig.	float4	6 Dez.Stellen
		float8	15 Dezimalstellen
date	YYYY-MM-DD Datumsformat	date	Datum, Datumformate mit SET DATESTYLE=Value einstellbar
time	HH-MM-SS Zeitformat	time	Uhrzeit, Auflösung 1 Mikrosekunde
char(m)	Zeichenkette mit fester Länge	char	ein Zeichen
varchar(m)	variable Länge, max. m Zeichen	varchar(n)	4+n Bytes
blob	Binary Large Object, wird für Texte gebraucht, "TINY", "", "LONG"	bytea
		money	4 Byte, -21474836,48 ... +21474836,47
		text	Variable Länge
		bool	Kann den Wert 't' oder 'f' annehmen