Using the Active Database
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Go Up to DSQL Limitations (Application Requirements)
A DSQL application can only work with one database at a time, even if the application attaches to multiple databases. All DSQL statements operate only on the currently active database, the last database associated with a handle in a SET DATABASE statement.
Embedded SQL statements within a DSQL application can operate on any open database. For example, all DSQL statements entered by a user at run time might operate against a single database specified by the user, but the application might also contain non-DSQL statements that record user entries in a log database.
For a complete discussion of SET DATABASE, see Working with Databases.