Using KSAM/XL and KSAM 64 (32650-90886)

Chapter 5 51

Reading File Data

Sequential Access by Partial Key Value

The FFINDBYKEY intrinsic can be used to point to those records that contain a common

portion of a key ﬁeld. The intrinsic parameters (

key value

key length

, and

relational

operator

) identify the partial value to be matched, the number of characters to be

compared in the key ﬁeld, and whether the record should equal the value or be greater

than the value.

Only the common portion of the key is speciﬁed in the

key value

ﬁeld. For example, to list

all records with a zip code beginning with 943 but ending in any combination of numbers,

943 is entered in the

key value

ﬁeld.

The

key length

parameter identiﬁes the portion of the key ﬁeld to be used in the

comparison. For example, to list all records with a zip code beginning with 943, a

key

length

of 3 would be speciﬁed. This means that only the ﬁrst three characters of the

ﬁve-character ﬁeld are used in the comparison.

The

relational operator

limits the operation to only those records that meet the

criteria. The relational operators that can be speciﬁed are 0 (equal to), 1 (greater than),

and 2 (equal to or greater than). Figure 5-3. searches for the ﬁrst occurrence of a record

containing a partial key of “M0”.

Figure 5-3. Partial Key Search Sample

fby_keyvalue := ’M0’;

fby_keylocation := 1;

fby_keylength := 2;

fby_relop := 0;

FFINDBYKEY(filenum,fby_keyvalue,fby_keylocation,fby_keylength,fby_relop);

lgth := FREAD(filenum,fr_record,fr_tcount);

To read all records containing “M0”, a series of freads would be issued and a comparison

made in the program to see when the key ﬁeld

did not

contain “M0” or the end of the ﬁle

reached.