3/1/2024 0 Comments Sqlight affinity varchar![]() ![]() In this case, the SQLite engine is compiled with SQLITE_ENABLE_COLUMN_METADATA defined (by default, this is True for Windows, and False for other platforms). If the type declaration contains parenthesis (to specify precision, for example VARCHAR(14)), SQLITE_TEXT is mapped to WideStringType.īlobType with a subtype of WideMemoSubTypeįireDAC uses the SQLite columns affinity: Listbox2.AddRow Str(c/c0,"#0.For dbExpress, the SQLite column affinities are mapped as follows:īlobType with a subtype of WideMemoSubType. Listbox1.AddRow Str(c/c0,"#0.0000")Īnd in the action event of the second button: SQLite uses dynamic typing the name of the declared data type does not matter: CREATE TABLE MyTable ( Col1 TEXT, - this is stored as a text value Col2 STRING, - so is this Col3 VARCHAR (1), - and this Col4 FLUFFY BUNNIES, - and this Col5, - and this Col6 INTEGER - and this, if the actual value is not a number ) The declared length is. The type affinity of a column is the recommended type for data stored in that column. : A column with an integer affinity works essentially the same as a numeric affinity. The INTEGER storage class, for example, includes 6 different integer datatypes of different lengths. To show what i mean make a new program with 2 listboxes and 2 buttons, in the action event of the first button put this code: SQLite supports the concept of 'type affinity' on columns. SQLite storage class is slightly more general than a datatype. There was said that this would be a random number but with every new start of the program it generates every time the same sequence of numbers. In the case of the Int64 the division by zero results in a ‘inf’ -value (infinity), but in the case of the currency the result is a ‘normal’ number that can be used in further calculations without ever been noticed. The currency datatype handles division by zero in a very strange manner and although there is said that the currency datatype is in fact a Int64 datatype, they are both handled different in case of division by zero. My advice would be to not use the currency datatype at all if you are not in full control of the calculations that are made with the data from the database. If the declared type for a column contains any of the strings “REAL”, “FLOA”, or “DOUB” then the column has REAL affinity. If the declared type for a column contains the string “BLOB” or if no type is specified then the column has affinity BLOB. Notice that the type VARCHAR contains the string “CHAR” and is thus assigned TEXT affinity. If the declared type of the column contains any of the strings “CHAR”, “CLOB”, or “TEXT” then that column has TEXT affinity. The important idea here is that the type is recommended, not required. The type affinity of a column is the recommended type for data stored in that column. If the declared type contains the string “INT” then it is assigned INTEGER affinity. In order to maximize compatibility between SQLite and other database engines, SQLite supports the concept of 'type affinity' on columns. The affinity of a column is determined by the declared type of the column, according to the following rules in the order shown: The value is a blob of data, stored exactly as it was input. The value is a text string, stored using the database encoding (UTF-8, UTF-16BE or UTF-16LE). Since type affinities are not part of the SQL standard, SQLite has a series of rules that attempt to map traditional column types to the most logical type. Each value is stored as the type provided, with no attempt to convert anything. The value is a floating point value, stored as an 8-byte IEEE floating point number. None: A column with a none affinity has no preference over storage class. The value is a signed integer, stored in 1, 2, 3, 4, 6, or 8 bytes depending on the magnitude of the value. I always use DOUBLE and have never had a problem…Įach value stored in an SQLite database (or manipulated by the database engine) has one of the following storage classes:
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