> For the complete documentation index, see [llms.txt](https://faris-shi84.gitbook.io/oracle-12c-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://faris-shi84.gitbook.io/oracle-12c-notes/appendix-terminology.md).

# Appendix: Terminology

`String Literal`: A string literal is a set of characters enclosed in single quotation marks (''); it’s interpreted as is, not treated as a keyword or command.

`Wildcard characters`: They are used to present one or more alphanumeric characters, The wildcard characters available for pattern search in Oracle 12c are the percent sign "%" and underscore symbol "\_".

`Escape Character`: It indicates when wildcard symbols should be used as literals rather than translated as wildcard characters. "\\"

`Database Object` is defined, and self-contained structure in Oracle 12C. For exmaple: Table, View, Constriant. It can be anything with a name and a defined structure.

`SCHEMA` indicates who own the table. if the person creating the table is also the person who owns the table, the `SCHEMA` can be omitted, the current username is assumed by default.

`Substitution Variable` in the SQL command instructs Oracle to substitute a value in place of the variable at the time the command is actually executed. "&"

`PseudoColumns`: data associated with table data, much like column, but not physical column stored in the database.

`ROWID`: the physical address of a table row.

`Cardinality`: to describe the level of distinct values in a table column. If a column contains many distinct values, it is described as having high cardinality.