Search results
Results from the WOW.Com Content Network
all rows for which the predicate in the WHERE clause is True are affected (or returned) by the SQL DML statement or query. Rows for which the predicate evaluates to False or Unknown are unaffected by the DML statement or query. The following query returns only those rows from table mytable where the value in column mycol is greater than 100.
The terms schema matching and mapping are often used interchangeably for a database process. For this article, we differentiate the two as follows: schema matching is the process of identifying that two objects are semantically related (scope of this article) while mapping refers to the transformations between the objects.
Joining data from multiple sources (e.g., lookup, merge) and deduplicating the data; Aggregating (for example, rollup – summarizing multiple rows of data – total sales for each store, and for each region, etc.) Generating surrogate-key values; Transposing or pivoting (turning multiple columns into multiple rows or vice versa)
The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.
Optionally, a column that defines the primary key of the composite data may also be specified: on parallel hardware, the column values are used to partition the index's contents across multiple disks. When the source tables are updated interactively by users, the contents of the join index are automatically updated.
Draped layers of merlot fabric brought some shape to the column dress, and Saldaña wrapped one piece around her shoulder to emphasize the design’s asymmetrical straps, as well as to create a ...
COST data by YCharts. 3. Value stocks increase in popularity. Many stocks now trade at premium prices thanks to the huge gains of the last couple of years. Sooner or later, though, investors will ...
Multiple companies and individuals have revealed plans to donate at the $1 million-level, including online retail giant Amazon, Ford Motor Company and hedge fund billionaire Ken Griffin. Some have ...