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Postgres-XL is based on Postgres-XC, an earlier distributed PostgreSQL system developed by NTT Data and EnterpriseDB. [4] In 2012, the cloud database startup StormDB [ 5 ] adopted Postgres-XC and developed some proprietary extensions and improvements to it. [ 6 ]
A table (called the referencing table) can refer to a column (or a group of columns) in another table (the referenced table) by using a foreign key. The referenced column(s) in the referenced table must be under a unique constraint, such as a primary key. Also, self-references are possible (not fully implemented in MS SQL Server though [5]).
Clearly creating a table (or a set of tables) with thousands of columns is not feasible, because the vast majority of columns would be null. To complicate things, in a longitudinal medical record that follows the patient over time, there may be multiple values of the same parameter: the height and weight of a child, for example, change as the ...
Data in child tables will appear to exist in the parent tables, unless data is selected from the parent table using the ONLY keyword, i.e. SELECT * FROM ONLY parent_table;. Adding a column in the parent table will cause that column to appear in the child table.
In situations where the number of unique values of a column is far less than the number of rows in the table, column-oriented storage allow significant savings in space through data compression. Columnar storage also allows fast execution of range queries (e.g., show all records where a particular column is between X and Y, or less than X.)
The following example of a SELECT query returns a list of expensive books. The query retrieves all rows from the Book table in which the price column contains a value greater than 100.00. The result is sorted in ascending order by title. The asterisk (*) in the select list indicates that all columns of the Book table should be included in the ...
Comma-separated values (CSV) is a text file format that uses commas to separate values, and newlines to separate records. A CSV file stores tabular data (numbers and text) in plain text, where each line of the file typically represents one data record.
Microsoft Excel 4/5/95 XLS, XLW, XLT Yes Yes Microsoft Excel 97–2003 XLS, XLW, XLT Yes Yes DocBook: XML Yes Yes since 1.1 WordPerfect: WPD Yes WordPerfect Suite 2000/Office 1.0 WPS Yes StarOffice StarWriter 3/4/5 SDW, SGL, VOR Yes Yes Ichitaro 8/9/10/11 JTD, JTT Yes ApportisDoc (Palm) PDB Yes Yes Requires Java Hangul WP 97 HWP Yes Microsoft ...