The following statement converts a string constant to an integer: SELECT CAST ( '100' AS INTEGER) Code language: SQL (Structured Query Language) ( sql ) Let’s take some examples of using the CAST operator to convert a value of one type to another. Notice that the cast syntax with the cast operator (::) is PostgreSQL-specific and does not conform to the SQL standard PostgreSQL CAST examples '0':: DATE Code language: SQL (Structured Query Language) ( sql ) See the following example: SELECT '100':: INTEGER, Then, specify the target data type to which you want to convert the result of the expression.īesides the type CAST syntax, you can use the following syntax to convert a value of one type into another: expression::type Code language: SQL (Structured Query Language) ( sql ).First, specify an expression that can be a constant, a table column, an expression that evaluates to a value.The following illustrates the syntax of type CAST: CAST ( expression AS target_type ) Code language: SQL (Structured Query Language) ( sql ) PostgreSQL provides you with the CAST operator that allows you to do this. There are many cases that you want to convert a value of one data type into another. Pairs with the same meaning (useful when some members are repeated).Summary: in this tutorial, we will show you how to use PostgreSQL CAST operator to convert a value of one type to another. Matching PostgreSQL enum labels as values, or a list of (member, label) Mapping should be a dictionary with Python enum members as keys and the PostgreSQL enum, or vice versa), you can specify the exceptions using the Have a different name, or if more than one Python enum should map to the same If the Python and the PostgreSQL enum don’t match 1:1 (for instance if members "SELECT pg_typeof( %(editor)s ), %(editor)s ". fetch ( conn, "user_role" ) > register_enum ( info, conn, UserRole ) > some_editor = info. execute ( "CREATE TYPE user_role AS ENUM ('ADMIN', 'EDITOR', 'GUEST')" ) > info = EnumInfo. > from enum import Enum, auto > from import EnumInfo, register_enum > class UserRole ( Enum ). If no enum is specified, a new Enum is created based on PostgreSQL enum labels into corresponding Python enum members. Mapping – Override the mapping between enum members and infoĪfter registering, fetching data of the registered enum will cast If None,Ī new enum will be generated and exposed as EnumInfo.enum. If None,Įnum – Python enum type matching to the PostgreSQL one. Info – The object with the information about the enum to register.Ĭontext – The context where to register the adapters. Register the adapters to load and dump a enum type. register_enum ( info : EnumInfo, context : Optional = None, enum : Optional ] = None, *, mapping : Optional, Sequence ] ] ] = None ) # Latter’s documentation for generic usage, especially theĪfter fetch(), it contains the labels definedĪfter register_enum() is called, it will contain the Python type EnumInfo ( name : str, oid : int, array_oid : int, labels : Sequence ) #ĮnumInfo is a subclass of TypeInfo: refer to the The registered PostgreSQL enum is loaded back as the registered PythonĬlass. fetch() andĮnums classes, both pure and mixed-in, are dumped by name. If the enum is registered (using EnumInfo. Of such enums you will have to find their OIDs using () PostgreSQL enums are loaded as Python strings. It’s dumped by default according to int rules). Mix-in enums are dumped according to their mix-in type (because a class MyIntEnum(int, Enum) is more specifically an int than an Enum, so Obtain a connection in a supported style using the options connectionĬhanged in version 3.1: In previous version dumping pure enums is not supported and raise a If your server is configured with different settings by default, you can With a different setting is not supported. IntervalStyle is postgres loading interval data in text format Representation in other formats is ambiguous.įurthermore, at the time of writing, the only supported value for The connection DateStyle is set to ISO format time and time zone Loading timestamp with time zone in text format is only supported if Implementing the added capability please see this example for a reference. Or the time 24:00 to 00:00) and write a subclass of the default loaders Instance mapping every value greater than to date.max, If you need to handle these values you can define your own mapping (for Loading these values will raise a DataError. Represented by the Python datetime objects:ĭates and timestamps after the year 9999, the special value “infinity” ĭates and timestamps before the year 1, the special value “-infinity” PostgreSQL date and time objects can represent values that cannot be fetchone () # UTC input datetime.datetime(2042, 7, 1, 14, 0, tzinfo=zoneinfo.ZoneInfo(key='Europe/Rome'))Ĭheck out the PostgreSQL documentation about timezones for all theĭetails. execute ( "SELECT ' 12:00Z'::timestamptz" ).
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