Preparing the Output XSQLDA to Read Data from a Blob

Go Up to Reading Data from a Blob

Most queries return one or more rows of data, referred to as a select-list. An output XSQLDA must be created to store the column data for each row that is fetched. For a Blob column, the column data is an internal Blob identifier (Blob ID) that is needed to access the actual data. To prepare the XSQLDA, follow these steps:

Declare a variable to hold the XSQLDA. For example, the following declaration creates an XSQLDA called out_sqlda:
```
XSQLDA *out_sqlda;
```
Allocate memory for the XSQLDA using the XSQLDA_LENGTH macro. The XSQLDA must contain one XSQLVAR substructure for each column to be fetched. The following statement allocates storage for an output XSQLDA (out_sqlda) with three XSQLVAR substructures:
```
out_sqlda = (XSQLDA *)malloc(XSQLDA_LENGTH(3));
```
Set the version field of the XSQLDA to SQLDA_CURRENT_VERSION, and set the sqln field of the XSQLDA to indicate the number of XSQLVAR substructures allocated:
```
out_sqlda->version = SQLDA_CURRENT_VERSION;
out_sqlda->sqln = 3;
```

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Preparing the SELECT Statement to Read Data from a Blob for Execution