ABAP HR infotype use and retrival

Question

Hi,
I am new to abap hr.In hr module we are using provide statement for retriving data.
My doubt is
1. why we are using provide instead of select?
2. Why we are using structure instead of direct tr table?
3. Why we are using infotype in hr and what is the use?
4. why we are retriving data using infotype in report instead of using tr.table using select?
5. What we have to specify if i want to retrive data from infotype?
6. We have to declare table/structure/infotype for retriving data?
7. And why we are specifying mode in declaration what is it mean?
if anybody knows tell me/send me the materials please.
Thanks,
Regards,
Nandha..

Answer 1

Hi Nandha,
The statements PROVIDE and ENDPROVIDE define a loop through a statement block. In this loop, any number of internal tables itab1 itab2 ... are processed together. A single table can appear several times. For every table itab you must specify a FIELDS clause. After FIELDS you must specify the character * for all components or a list comp1 comp2 ... for specific components of the relevant table. The names of the components comp1 comp2 ... can only be specified directly.
To be able to process internal tables using PROVIDE, all tables itab1 itab2 ... must be fully typed index tables and contain two special columns that have the same data type (d, i, n, or t) for all relevant tables. For every table you must specify the names intliml1 intliml2 ... and intlimu1 intlimu2 ... of these columns using the addition BOUNDS.
Eg:
PROVIDE FIELDS {*|{comp1 comp2 ...}}
               FROM itab1 INTO wa1 VALID flag1
               BOUNDS intliml1 AND intlimu1
               [WHERE log_exp1]
        FIELDS {*|{comp1 comp2 ...}}
               FROM itab2 INTO wa2 VALID flag2
               BOUNDS intliml2 AND intlimu2
               [WHERE log_exp2]
        BETWEEN extliml AND extlimu
        [INCLUDING GAPS].
ENDPROVIDE.