Search results
Results From The WOW.Com Content Network
Correlated subqueries may appear elsewhere besides the WHERE clause; for example, this query uses a correlated subquery in the SELECT clause to print the entire list of employees alongside the average salary for each employee's department.
The number 0, the strings "0" and "", the empty list (), and the special value undef evaluate to false. [8] All else evaluates to true. Lua has a Boolean data type, but non-Boolean values can also behave as Booleans. The non-value nil evaluates to false, whereas every other data type value evaluates to true.
A number of companies offer proprietary tools for PostgreSQL. They often consist of a universal core that is adapted for various specific database products. These tools mostly share the administration features with the open source tools but offer improvements in data modeling , importing, exporting or reporting.
According to PostgreSQL v.9 documentation, an SQL window function "performs a calculation across a set of table rows that are somehow related to the current row", in a way similar to aggregate functions. [7] The name recalls signal processing window functions. A window function call always contains an OVER clause.
Another recent idea is the similarity join. When matching database relates to a large scale of data, the O(mn) time with the dynamic programming algorithm cannot work within a limited time. So, the idea is to reduce the number of candidate pairs, instead of computing the similarity of all pairs of strings.
If there are too few letters in the word to assign three numbers, append zeros until there are three numbers. If there are four or more numbers, retain only the first three. Using this algorithm, both "Robert" and "Rupert" return the same string "R163" while "Rubin" yields "R150".
So far PostgreSQL is the only vendor to have announced a live product with this specific feature, in PostgreSQL 9.5. [ 3 ] [ 4 ] Other vendors have described some similar features, [ 2 ] including Oracle , [ 5 ] [ 6 ] Netezza 'zone maps', [ 7 ] Infobright 'data packs', [ 8 ] MonetDB [ 9 ] and Apache Hive with ORC/Parquet.
PostgreSQL and some other databases have support for foreign schemas, which is the ability to import schemas from other servers as defined in ISO/IEC 9075-9 (published as part of SQL:2008). This appears like any other schema in the database according to the SQL specification while accessing data stored either in a different database or a ...