Expression Editor
The Expression Editor helps users enter and validate SQL sub expressions (such as WHERE
clauses for filters). Expression Editor displays the available attributes, provides a selection of functions and commonly used operators, and validates expressions.
Expression Editor has the following components:
- Attributes tab:
Browse attributes in the source table or view. Double-click an attribute to insert it into expression at the current character position, or to replace characters that you selected before the replace.
- Functions tab:
Browse commonly used SQL functions. Expand a folder to list the functions. Double-click a function to insert it into expression at the current character position, or to replace characters that you selected before the replace.
- Column Name: The column name for the new column. The wizard provides a default name that you can change. This field is visible only when dialog is launched to create a new column.
- Expression area: The expression is displayed in this area as it is created. You can type into this area.
- Commonly-used operator buttons below the Expression area: Click the appropriate button to insert <, >, <=, >=, != (not equal to), =,
Or
, And
, (, ), ||, +, -, *, /, or % into the expression at the current character position. If you prefer, you can type an operator directly into the Expression area.
- Validation Results text area (read-only) and Validate: Click Validate to validate the expression. The results appear in Validation Results.
When you have finished creating the expression, click OK to return to the calling window. If you have not already validated the name and/or expression by clicking Validate, the wizard performs validation.
Functions
The Expression Editor supports a wide variety of functions that can be applied to character, numeric, and date data. There are functions that support most of the common data preprocessing required for data mining, including missing values treatment. To see a list of the available functions, expand the category of interest.
Functions are divided into the following categories:
- Character (concatenate, trim, length, substring, etc.)
- Conversion (convert to character, date, number, etc.)
- Date (calculate next day, insert time stamp, truncate, round, etc.)
- Numeric (absolute value, ceiling, floor, trigonometric functions, hyperbolic functions, logarithms, exponentials, etc.)
- Analytical (common statistical functions, such as average, variance, etc.)
NULL
Value Substitution (for dates, characters, and numbers)
The notation for the functions is that of SQL. For more information about these functions, see the Oracle Database SQL Reference.
Validation
Both the column name and the expression are validated.
The column name is checked for the following:
- The new name does not already exist in source data.
- The new name is not already defined among the newly defined names in the current wizard session.
- The new name is a valid identifier; see Names of Data Mining Objects.
The expression is validated; you are informed of any problems.
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