Runtime Character Conversion
Automatic conversion occurs between Ingres character string values and COBOL character variables (alphabetic, alphanumeric, and alphanumeric edited data items). There are four string-valued Ingres objects that can interact with character variables:
• Ingres names, such as form and column names
• Database columns of type c or char
• Database columns of type text or varchar
• Form fields of type c
Several considerations apply when dealing with character string conversions, both to and from Ingres.
The conversion of COBOL character variables used to represent Ingres names is simple: trailing blanks are truncated from the variables, because the blanks make no sense in that context. For example, the string constants "empform " and "empform" refer to the same form and "employees " and "employees" refer to the same database table.
The conversion of other Ingres objects is a bit more complicated. First, the storage of character data in Ingres differs according to whether the medium of storage is a database column of type c or char, a database column of type text or varchar, or a character-type form field. Ingres pads columns of type c and char with blanks to their declared length. Conversely, it does not add blanks to the data in columns of type text, or varchar in form fields.
Second, the COBOL convention is to blank-pad fixed-length character strings. For example, the character string "abc" may be stored in a COBOL PIC X(5) data item as the string "abc" followed by two blanks.
When character data is retrieved from a database column or form field into a COBOL character variable and the variable is longer than the value being retrieved, the variable is padded with blanks. If the variable is shorter than the value being retrieved, the value is truncated. You must always ensure that the variable is at least as long as the column or field, in order to avoid truncation of data. You should note that, when a value is transferred into a data item from a Ingres object, it is copied directly into the variable storage area without regard to the COBOL special insertion rules.
When inserting character data into an Ingres database column or form field from a COBOL variable, note the following conventions:
• When data is inserted from a COBOL variable into a database column of type c or char and the column is longer than the variable, the column is padded with blanks. If the column is shorter than the variable, the data is truncated to the length of the column.
• When data is inserted from a COBOL variable into a database column of type text or varchar and the column is longer than the variable, no padding of the column takes place. Furthermore, by default, all trailing blanks in the data are truncated before the data is inserted into the text or varchar column. For example, when a string "abc" stored in a COBOL PIC X(5) data item as "abc " (refer to above) is inserted into the text or varchar column, the two trailing blanks are removed and only the string "abc" is stored in the database column. To retain such trailing blanks, you can use the Ingres notrim function. It has the following syntax:
notrim(charvar)
where charvar is a character variable. An example that demonstrates this feature follows this section. If the text or varchar column is shorter than the variable, the data is truncated to the length of the column.
• When data is inserted from a COBOL variable into a c form field and the field is longer than the variable, no padding of the field takes place. In addition, all trailing blanks in the data are truncated before the data is inserted into the field. If the field is shorter than the data (even after all trailing blanks have been truncated), the data is truncated to the length of the field.
When comparing character data in a Ingres database column with character data in a COBOL variable, note the following convention:
• When comparing data in a c, character, or varchar database column with data in a character variable, all trailing blank are ignored. Initial and embedded blanks are significant in character, text, and varchar; they are ignored in c.
Important! As previously described, the conversion of character string data between Ingres objects and COBOL variables often involves the trimming or padding of trailing blanks, with resultant change to the data. If trailing blanks have significance in your application, give careful consideration to the effect of any data conversion.
The Ingres date data type is represented as a 25-byte character string: PIC X(25).
The program fragment in the following examples demonstrates the notrim function and the truncation rules explained above:
UNIX:
DATA DIVISION.
WORKING-STORAGE SECTION
## 01 ROW PIC S9(4) USAGE COMP.
## 01 DATA PIC X(7).
## DECLARE.
PROCEDURE DIVISION.
BEGIN.
## MOVE "abc " TO DATA.
* Set up the table for testing
## CREATE texttype (#row = i2, #data = text(10))
* The first APPEND adds the string "abc" (blanks
* truncated)
## APPEND TO texttype (#row = 1, #data = data)
* The second APPEND adds the string "abc ",
* with 4 trailing blanks
## APPEND TO texttype (#row = 2, #data = NOTRIM(data))
* The RETRIEVE will get the second row because
* the NOTRIM function in the previous APPEND
* caused trailing blanks to be inserted as data.
## RETRIEVE (row = texttype.#row)
## WHERE length(texttype.#data) = 7
DISPLAY "Row found = " ROW.
VMS:
DATA DIVISION.
WORKING-STORAGE SECTION
## 01 ROW PIC S9(4) USAGE COMP.
## 01 DATA PIC X(7).
## DECLARE.
PROCEDURE DIVISION.
BEGIN.
* Set up the table for testing
## CREATE texttype (#row = i2, #data = text(10))
* The first APPEND adds the string "abc"
* (blanks truncated)
## APPEND TO texttype (#row = 1, #data = data)
* The second APPEND adds the string "abc ", with
* 4 trailing blanks
## APPEND TO texttype (#row = 2, #data = NOTRIM(data))
* The RETRIEVE will get the second row because
* the NOTRIM function in the previous APPEND
* caused trailing blanks to be inserted as data.
## RETRIEVE (row = texttype.#row)
## WHERE length(texttype.#data) = 7
DISPLAY "Row found = " ROW.
