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SQL-92 was the third revision of the SQL database query language. Unlike SQL-89, it was a major revision of the standard. Aside from a few minor incompatibilities, the SQL-89 standard is forward-compatible with SQL-92. The standard specification itself grew about five times compared to SQL-89.
Hash functions: based on the content of the identified object, ensuring that equivalent objects use the same UID. Random number generator : based on random process. names or codes allocated by choice which are forced to be unique by keeping a central registry such as the EPC Information Services .
Then 6 or 7 bits are replaced by fixed values, the 4-bit version (e.g. 0011 2 for version 3), and the 2- or 3-bit UUID "variant" (e.g. 10 2 indicating a RFC 9562 UUIDs, or 110 2 indicating a legacy Microsoft GUID). Since 6 or 7 bits are thus predetermined, only 121 or 122 bits contribute to the uniqueness of the UUID.
A surrogate key is frequently a sequential number (e.g. a Sybase or SQL Server "identity column", a PostgreSQL or Informix serial, an Oracle or SQL Server SEQUENCE or a column defined with AUTO_INCREMENT in MySQL). Some databases provide UUID/GUID as a possible data type for surrogate keys (e.g. PostgreSQL UUID [3] or SQL Server ...
In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates (a duplicate entry is not valid in a unique column). Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not typically used to join multiple tables.
Title Authors ----- ----- SQL Examples and Guide 4 The Joy of SQL 1 An Introduction to SQL 2 Pitfalls of SQL 1 Under the precondition that isbn is the only common column name of the two tables and that a column named title only exists in the Book table, one could re-write the query above in the following form:
Sophomore wide receiver Eric Singleton Jr., one of the top skill-position targets in the transfer portal, is headed to Auburn to catch passes from Jackson Arnold.
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). [3]