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Friday, January 9, 2009

PostgreSQL's ecpg follows the ANSI standard for embedding SQL in C code, and what follows will be familiar to programmers who have used systems such as Oracle's PRO*C or Informix's ESQL-C. At the time of writing some of the less used features of embedded SQL are not supported, and the standard documentation for ecpg that ships with PostgreSQL is somewhat limited.Since we have now worked through many of the basics of SQL, this section will actually be quite short. The first problem that has to be tackled is how to delimit sections in the file that the ecpg pre-processor needs to process. This is done with the special sequence in the source that starts 'exec sql', then contains the SQL you want to execute, and ends with a ';'. Depending on the exact syntax, as we shall see in a moment, this can either be a single line that needs to be processed, or it can be used to mark a section that needs pre-processing. If we want to write a simple C program that performs a single UPDATE statement in the middle of some C code, we need to do only one thing in the source code - embed the UPDATE SQL statement....


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