mySQL C API multiple statements

Question

So I'm building a C program that connects to a mySQL database. Everything worked perfectly. Then, to save on number of queries, I decided that I would like to execute 10 statements at a time. I set the "CLIENT_MULTI_STATEMENTS" flag in the connection, and separated my statements by semicolons.

When I execute the first batch of 10 statements, it succeeds and mysql_real_query() returns a 0.

When I try the second batch though, it returns a "1" and doesn't work. Nowhere can I find what this "1" error code means, so I was hoping someone may have run into this problem before.

Please note that these are all UPDATE statements, and so I have no need for result sets, it's just several straight-up calls to mysql_real_query().

Mel · Accepted Answer · 2011-05-09 00:26:21Z

3

It's not clear from the documentation whether the errors this function can cause are returned or not, but it should be possible to obtain the actual error using mysql_error().

My guess is that you still have to loop through the result sets whether you're interested in them or not.`

answered May 9, 2011 at 0:26

Mel

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Femi · Accepted Answer · 2011-05-09 00:24:44Z

Are these prepared statements? If that's the case then you can't use CLIENT_MULTI_STATEMENTS.

Also, note (from http://dev.mysql.com/doc/refman/5.5/en/c-api-multiple-queries.html) that:

After handling the result from the first statement, it is necessary to check whether more results exist and process them in turn if so. To support multiple-result processing, the C API includes the mysql_more_results() and mysql_next_result() functions. These functions are used at the end of a loop that iterates as long as more results are available. Failure to process the result this way may result in a dropped connection to the server.

You have to walk over all the results, regardless of whether or not you care about the values.

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