Comparison of database column types in MySQL, PostgreSQL, and SQLite? (Cross-Mapping)
I am trying to find some way to relate column types across the the most used Databases: MySQL, PostgreSQL, and SQLite.
Here is what I have so far, but I'm afraid it's not done and I need some people with more experience to help me finish any missing types.
MySQL PostgreSQL SQLite
TINYINT SMALLINT INTEGER
SMALLINT SMALLINT
MEDIUMINT INTEGER
BIGINT BIGINT
BIT BIT INTEGER
_______________________________________________________
TINYINT UNSIGNED SMALLINT INTEGER
SMALLINT UNSIGNED INTEGER
MEDIUMINT UNSIGNED INTEGER
INT UNSIGNED BIGINT
BIGINT UNSIGNED NUMERIC(20)
_______________________________________________________
DOUBLE DOUBLE PRECISION REAL
FLOAT REAL REAL
DECIMAL DECIMAL REAL
NUMERIC NUMERIC REAL
_______________________________________________________
BOOLEAN BOOLEAN INTEGER
_______________________________________________________
DATE DATE TEXT
TIME TIME
DATETIME TIMESTAMP
_______________________________________________________
TIMESTAMP DEFAULT TIMESTAMP DEFAULT TEXT
NOW() NOW()
_______________________________________________________
LONGTEXT TEXT TEXT
MEDIUMTEXT TEXT TEXT
BLOB BYTEA BLOB
VARCHAR VARCHAR TEXT
CHAR CHAR TEXT
_______________________________________________________
columnname INT columnname SERIAL INTEGER PRIMARY
AUTO_INCREMENT KEY AUTOINCREMENT
Answer
List of things I'd do differently:
MEDIUMINT in MySQL is an odd duck (3 bytes). I would avoid it, but otherwise map it to INTEGER too.
The MySQL BOOLEAN (alias BOOL, alias TINYINT(1) ) is not compatible with the pg boolean type. You may or may not be able to port apps depending on what they use as boolean literals. In MySQL, TRUE and FALSE map to 1 and 0 integer values. It looks like the pg BOOLEAN type uses string literal notation. So apps may or may not be portable - at least it is no drop in replacement.
Finally, for the last line in your tabl I think the SQLite phrase should read:
INTEGER PRIMARY KEY AUTOINCREMENT
This is roughly equivalent to
BIGINT PRIMARY KEY AUTO_INCREMENT
in MySQL. In postgres, the SERIAL datatype results in an INTEGER column, and this will about the same as MySQL's
INTEGER PRIMARY KEY AUTO_INCREMENT
Postgres also has a BIGSERIAL type, which is the same as SERIAL but with a BIGINT type instead of an INT type.
What I missed:
I am missing INTEGER (alias INT) for MySQL. It is comparable to INTEGER in pg. Very important omissions: VARCHAR and CHAR. Semantically, VARCHAR in MySQL and PG, and CHAR in MySQL and PG are the same, but in MySQL these types have a much shorter maximum length. In MySQL these types can have a maximum of a little less than 64kb, in pg 1Gb (bytes). The actual length specifier is expressed in the number of characters, so if you have a multi-byte character set, you have to divide the maximum lenght by the maximum number of characters to get the theoretical maximum length specified for that characterset. In SQLite, VARCHAR and CHAR map both to TEXT
The BIT datatypes in MySQL and PG have roughly the same semantics, but in MySQL the maximum length of the BIT data type is 64 (bits)
I think the MySQL VARBINARY data type is best comparable to PG's BYTEA datatype. (but indeed MySQL's BLOB types also map to that)
The FLOAT type in MySQL should be equivalent to REAL in postgres (and REAL in SQLite too) The DECIMAL type in MySQL is equivalent to DECIMAL in postgres, except that in postgres, the type does not impose an arbtrary limit on the precision, whereas in MySQL the maximum precision is (i believe) 70. (that is, 70 number positions) For both MySQL and Postgres, NUMERIC is an alias for the DECIMAL type.