For a parameterized SQL statement, your DataBlade®
API module must perform
the following steps:
Specify input parameters in the text of the SQL statement.
Send the SQL statement to the database server for parsing.
Provide input-parameter values when the SQL statement executes.
The mi_prepare() statement performs these first
two steps for a parameterized statement.
The mi_exec_prepared_statement() and mi_open_prepared_statement() functions
assign values to input parameters when they send a parameterized SQL
to the database server for execution. To provide a value for an input
parameter, you pass information in several parallel arrays:
Parameter-value array
Parameter-value type array
Parameter-value length array
Parameter-value null array
These input-parameter value arrays are similar to the input-parameter
arrays in the statement descriptor (see Input-parameter arrays in the statement descriptor ). They
have an element for each input parameter in the prepared statement.
However, they are unlike the input-parameter arrays in the statement
descriptor in the following ways:
An input-parameter value array describes the actual value for
an input parameter.
An input-parameter array describes the column
with which the input parameter is associated.
You must allocate and manage an input-parameter value array.
The DataBlade®
API does
not provide accessor functions for input-parameter value arrays. For
each input parameter, your DataBlade®
API module must declare,
allocate, and assign a value to the array.
All of the input-parameter-value arrays have zero-based indexes.
The following figure shows how the information at index position 1 of
these arrays holds the input-parameter-value information for the second
input parameter of a prepared statement.
Figure 1. Arrays for initialization
of input parameters
You specify the number of input-parameter values in the input-parameter
value arrays with the nparams argument of mi_exec_prepared_statement() or mi_open_prepared_statement().
