The readtext command provides a way to retrieve text, unitext, and image values to retrieve only a selected portion of a column’s data. readtext requires the name of the table and column, the text pointer, a starting offset within the column, and the number of characters or bytes to retrieve. This example finds six characters in the copy column in the blurbs table:
declare @val binary(16) select @val = textptr(copy) from blurbs where au_id = "648-92-1872" readtext blurbs.copy @val 2 6 using chars
In the example, after the @val local variable has been declared, readtext displays characters 3 – 8 of the copy column, since the offset was 2.
Instead of storing potentially large text, unitext, and image data in the table, Adaptive Server stores it in a special structure. A text pointer (textptr) which points to the page where the data is actually stored is assigned. When you retrieve data using readtext, you actually retrieve textptr, which is a 16-byte varbinary string. To avoid this, declare a local variable to hold textptr, and then use the variable with readtext, as in the example above.
See “Text functions used for text, unitext, and image data” for an advanced discussion of the readtext command.
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