Most DBAPIs have built in support for the datetime DateTime ( timezone = False ) ¶ĭate and time types return objects from the Python datetime This can be useful for calling setinputsizes(), for example. Return the corresponding type object from the underlying DB-API, if “literal_binds” flag, typically used in DDL generation as wellĪs in certain scenarios where backends don’t accept bound parameters.Ĭlass ( sqlalchemy.types._LookupExpressionAdapter, ) method. This function is used when the compiler makes use of the To be rendered directly without using binds. Return a conversion function for processing literal values that are Parameters :ĭialect ¶ – Dialect instance in use. If processing is not necessary, the method should return None. Returns a callable which will receive a bind parameter valueĪs the sole positional argument and will return a value to Return a conversion function for processing bind values. Name ¶ – if a CHECK constraint is generated, specify On the table that ensures 1 or 0 as a value. Is generated as an int/smallint, also create a CHECK constraint _init_ ( create_constraint = True, name = None, _create_events = True ) ¶Ĭreate_constraint ¶ – defaults to True. Typically generates a BIGINT in DDL, and otherwise acts likeĬlass (, , ) method. The base for all string and character types. Mark a type as possibly requiring schema-level DDL for usage. Holds Python objects, which are serialized using pickle. NUMERIC, FLOAT, DECIMAL, and other variants. Refers to the return type of the MATCH operator.īase for non-integer numeric types, such as Type representing floating point types, such as FLOAT or REAL. SQL Standard and Multiple Vendor Types and the other sections of this chapter. Type is emitted in CREATE TABLE, such as VARCHAR see SQLAlchemy will choose the bestĭatabase column type available on the target database when issuing aĬREATE TABLE statement. Generic types specify a column that can read, write and store a To Integer() with no construction arguments in this case. Typically accept a type class or instance Integer is equivalent Information when issuing a CREATE TABLE statement and will use itĪgain when reading back rows SELECTed from the database.įunctions that accept a type (such as Column()) will SQLAlchemy will use the Integer and String(32) type Column ( 'id', Integer, primary_key = True ). In that case, a FK would be better but the base table would have to have 'unknown' as a default type and define game_rating as NOT NULL. OK game_rating may be a bad example since ESRB could create more game ratings. you can allow for NULL (Example : game_rating ENUM('EC','E','E10+','T','M','A') NULL This allows a new game to be entered into a table without a default rating).Otherwise, bait-and-switch methods of maintenance would have to accompany the use of the ENUM. its portability must always be based on logcial dumps of the table, never physical.it will never likely experience redefinition.it must represent a type that is never changed.the type you are representing is local to the table only.Here is what should be considered about ENUM usage: Hence, this would not be suitable for ENUMs because the constraint checking would have to be done in your application rather than in the database. Such concerrns would definitely apply if using ENUM.įoreign Key Constraints would server to protect a row from absorbing invalid types. In addition, you would not be worried about those values matching up exactly with the base table definition of the type. Just by adding new entries into a table with the types needed, keys can be passed around to other tables without worrying about the underlying value being properly represented in the foreign tables. Using foreign keys makes a great deal of sense when you know that the types you are establishing can be extended, reduced, or altered. While there are bait-and-switch tricks you can perform to extend a range for an ENUM, those same tricks become very cumbersome (maybe even impossible) if you want to do other things such as reducing or altering an ENUM range. Once those values are put in place, it can be rather challenging to perform any kind of simple maintenance should you want to redefine the ENUM range. When using ENUM to have a range of values, you have to properly plan what values you will use.
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