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It is a collection of character data in a database management system, usually stored in a separate location that is referenced in the table itself. Oracle and IBM Db2 provide a construct explicitly named CLOB, [ 1 ] [ 2 ] and the majority of other database systems support some form of the concept, often labeled as text , memo or long character ...
Varchar fields can be of any size up to a limit, which varies by databases: an Oracle 11g database has a limit of 4000 bytes, [1] a MySQL 5.7 database has a limit of 65,535 bytes (for the entire row) [2] and Microsoft SQL Server 2008 has a limit of 8000 bytes (unless varchar(max) is used, which has a maximum storage capacity of 2 gigabytes).
If a table contains big variable-length columns (BLOB or TEXT) it cannot use the FIXED format. DYNAMIC: Variable-length columns do not have a fixed length size. This format is a bit slower to read but saves some space on disk. COMPRESSED: Compressed tables can be created with a dedicated tool while MySQL is not running, and they are read-only.
Informix v12.10 and later versions support using sharding techniques to distribute a table across multiple server instances. A distributed Informix database has no upper limit on table or database size. Note (13): Informix DECIMAL type supports up to 32 decimal digits of precision with a range of 10 −130 to 10 125. Fixed and variable ...
Expressions, which can produce either scalar values, or tables consisting of columns and rows of data; Predicates, which specify conditions that can be evaluated to SQL three-valued logic (3VL) (true/false/unknown) or Boolean truth values and are used to limit the effects of statements and queries, or to change program flow.
For example, a table of 128 rows with a Boolean column requires 128 bytes a row-oriented format (one byte per Boolean) but 128 bits (16 bytes) in a column-oriented format (via a bitmap). Another example is the use of run-length encoding to encode a column.
Most database and spreadsheet programs are able to read or save data in a delimited format. Due to their wide support, DSV files can be used in data exchange among many applications. A delimited text file is a text file used to store data, in which each line represents a single book, company, or other thing, and each line has fields separated ...
At the very least, the attribute definitions table would contain the following columns: an attribute ID, attribute name, description, data type, units of measurement, and columns assisting input validation, e.g., maximum string length and regular expression, maximum and minimum permissible values, set of permissible values, etc.