Testing and searching for elements of lists. "Getting Pieces of Lists" discusses how to extract pieces of lists based on their positions or indices. Mathematica also has ...

DatabaseExplorer[] launches a graphical user interface to DatabaseLink.

SQLRollbackTransaction[conn] terminates an SQL transaction. SQLRollbackTransaction[conn, savepoint] returns to an SQLSavepoint.

SQLServerLaunch[{name -> location, ...}] launches a database server that hosts access to the databases specified in the parameters.

SQLSetSavepoint[conn, name] creates a savepoint to be used as part of an SQL transaction.

AddPeriodical[expr, interval] adds the computation expr to the set of operations that are periodically performed automatically.

FrontEndSharedQ[link] returns True if the front end is being shared with a specified link, and returns False otherwise.

GetJavaException[] returns the Java Exception object that was thrown in the most recent call from Mathematica to Java.

JavaObject[] is used to denote an expression that refers to an object residing in Java.

LoadedJavaObjects[] returns a list of the Java objects that have been sent to Mathematica (and not yet released with ReleaseJavaObject).