Wavetronix Command Translator (CMD-DT) - User Guide Manuel d'utilisateur télécharger pdf (Page 125)

124 CHAPTER 11  TASKBUILDER SUB-WINDOWS

 Select the desired source column then drag the cursor from the source column to the

desired destination column. A blue guideline will appear to show the mapping line as

it goes across the screen.

Below is a list of rules concerning column mappings:

 Multiple Source Columns to Destination Columns – Multiple source columns may

NOT map to the same destination column. If a destination column already has a map-

ping associated with it, attempting to create another one will result in an error. You can,

however, map one source column to two or more dierent destination columns.

 Type Compatibility – TaskBuilder will automatically check for type compatibility and

will show an error message if two types are incompatible. Conversions exist between

many dierent data types; columns do not have to be the same type to be compatible.

Any Source column can be mapped to a String column. Number columns can be con-

verted to other number columns, but there may be some data loss. A sub-window will

inform you when there is a possibility of data loss or when a conversion is not allowed.

 Data Loss – It is possible to map larger columns into smaller ones (i.e. a 32-bit number

into a 16-bit number, or a oating point decimal number into an integer). However,

this creates the possibility of data loss because the number is truncated to t into a

smaller space. When this type of mapping is formed, TaskBuilder will create the map-

ping but will also show a message box warning of the potential for data loss. Text col-

umns within databases will commonly have xed-length designations which deter-

mine a max length for the text value. Copying text from a source column with a longer

text eld to a destination column with a shorter text eld can also lead to data loss

when the task is run and the source text is truncated.

 Unsafe Mappings – Some mappings are considered valid from a TaskBuilder perspec-

tive but may lead to errors at run-time when the task is executed. A mapping of a text

string column to a numerical column, for example, requires that all the text strings in

the source column be in numerical form that can be converted directly to numbers.

Any non-numeric text strings in the source table will cause the task to fail when run.

Default Values

A complete mapping requires values for each column in the destination table. A default

value will need to be provided when destination columns do not have a mapping to any

source column. is default value will be inserted into the column for each data row copied

over from the source database. TaskBuilder does not currently support mapping columns

from two or more dierent source tables into one destination table. For these transforma-

tions, a DB-to-Data-to-DB task will need to be created (see Appendix A).

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Wavetronix Command Translator (CMD-DT) - User Guide Manuel d'utilisateur Page 125