ROLLBACK This command undoes (Kids web site) any database changes not yet
ROLLBACK This command undoes any database changes not yet committed to the database using the COMMIT command. SDK Software development kit is a tool containing a programming language (Java, for example). SDKs are often used to build applications software. Secondary Index See Alternate index. SELECT command A command used to execute a query on a database. A SELECT command contains all the fields to be retrieved from tables. Additionally, a SELECT command can have optional additions used to perform special alterations to queries, such as filtering using a WHERE clause, and sorting using an ORDER BY clause. Self join Joins records in a table to the same table. Typically used for a table containing hierarchically structured records, such as a family tree. Semi-join Join two tables using a subquery, but not necessarily returning any field values to the calling query. Semi-joins occur when using IN and EXISTS operators. Sequence Allows automated generation of sequences of numbers, usually one after the other, such as 101, 102, 103, and so on. Some database engines call these auto counters. Simple datatype A term used to describe the most basic of datatypes, containing a simple value, such as an integer or a string. Snowflake schema A data warehouse, single fact table structure, with dimension tables in multiple layered hierarchies of dimensional tables. Sorted query See ORDER BY clause. SQL See Structured Query Language. Standby database A failover database. A standby database has minimal activity, usually only adding new records, changing existing records, and deleting existing records. Some database engines, however, allow standby databases to be utilized as secondary, active database platforms. Star schema A single fact table surrounded by a single hierarchical layer of dimensional tables, in a data warehouse database. Static data Data that does not change significantly. Stored function The same as a stored procedure, except that it returns a single value. Stored procedure Also called a database procedure, a chunk of code stored within and executed from within a database, typically on data stored in a database (but not always). String A simple datatype containing a sequence of alphanumeric characters. 417 Glossary
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