Pointer Usage with BASIC Variables
In order to fill an element of the sqlvar array, you must set the type information and assign a valid address to sqldata. The address must be that of a legally declared variable. If the element is nullable then the corresponding sqlind member must point at a legally declared null indicator variable.
Because both the sqldata and sqlind members of the sqlvar group are declared as long integers, you must assign integer values to them. This requires the use of the BASIC loc function.
For example, the following program fragment sets the type information of and points at a 4-byte integer variable, an 8-byte nullable floating-point variable, and an sqllen-specified character sub-string. This example demonstrates how a program can maintain a pool of available variables, such as large arrays of a few different typed variables and a large string space. When a variable is chosen from the pool the next available spot is incremented:
exec sql include sqlda
declare iisqlda sqlda
...
! Numeric and string 'pool' declarations
declare word constant MAX_POOL = 50
declare word ind_store(MAX_POOL) ! Indicators
declare word current_ind
declare long int4_store(MAX_POOL) ! Integers
declare word current_int
declare double flt8_store(MAX_POOL) ! Floats
declare word current_flt
declare string char_store(3000) = 1 ! String buffer
declare word current_chr
declare word need_len
...
!
! Note that if SQLD is set to 3 we use SQLVAR elements ! 0 through 2
!
sqlda::sqlvar(0)::sqltype = IISQ_INT_TYPE ! 4-byte integer
sqlda::sqlvar(0)::sqllen = 4
sqlda::sqlvar(0)::sqldata = loc(int4_store(current_int))
sqlda::sqlvar(0)::sqlind = 0
current_int = current_int + 1 ! Update integer pool
sqlda::sqlvar(1)::sqltype = -IISQ_FLT_TYPE ! 8-byte null float
sqlda::sqlvar(1)::sqllen = 8
sqlda::sqlvar(1)::sqldata = loc(float8_store(current_flt))
sqlda::sqlvar(1)::sqlind = loc(ind_store(current_ind))
current_flt = current_flt + 1 ! Update float and
current_ind = current_ind + 1 ! indicator pool
!
! SQLLEN has been assigned by DESCRIBE to be the length ! of a specific
! result column. This length is used to pick off a sub-string out of
! a large string space.
!
need_len = sqlda::sqlvar(2)::sqllen
sqlda::sqlvar(2)::sqltype = IISQ_CHA_TYPE
sqlda::sqlvar(2)::sqldata = loc(char_store(current_chr))
sqlda::sqlvar(2)::sqlind = 0
current_chr = current_chr + need_len ! Update char pool
...
Of course, in the above example, verification of enough pool storage must be made before each cell of the different arrays is referenced in order to prevent
sqldata and
sqlind from pointing at undefined storage. For demonstrations of this method, see
The SQL Terminal Monitor Application) and (see page
A Dynamic SQL/Forms Database Browser in this chapter.
The IISQ_HDLR_TYPE is a host language type that is used for transmitting data to and from Ingres. Because it is not an Ingres data type, it will never be returned as a data type from the describe statement.