boolmysql_stmt_bind_named_param(MYSQL_STMT *stmt, MYSQL_BIND *binds, unsigned n_params, const char **names)mysql_stmt_bind_named_param() sets up unnamed and named (query attributes) bind parameters for prepared statements.
This function supersedes the oldmysql_stmt_bind_param() function, which supported only unnamed parameters, and which has since been removed.
Arguments:
stmt: The statement handler. Statements must be prepared withmysql_stmt_prepare().binds: An array of named and unnamed bind parameters. In the absence of named parameters, pass inNULLas the array of bind parameter names.n_params: Number of items within arrays.names: An array of bind parameter names.
mysql_stmt_bind_named_param() requires an input of arrayMYSQL_BIND structures and the matching names array. It succeeds without any effect (in corner cases) if the bind argument count parameter is zero or if the bind array pointer isNULL. It fails if an invalidMYSQL_BIND type is used for any bind parameter arguments.
To store both named and unnamed bind user variables, callmysql_stmt_bind_named_param() aftermysql_stmt_prepare(). Subsequent to binding the variables, you can set and change them repeatedly.
Additional actions to consider are:
Execute the statement using
mysql_stmt_execute().Reset the statement using
mysql_stmt_reset()or reprepare it with another query usingmysql_stmt_prepare().Close the statement with
mysql_stmt_close().
For a description of the members of theMYSQL_STMT andMYSQL_BIND structure and how they should be set to provide input values, seeSection 6.2, “C API Prepared Statement Data Structures”.
The conversion is not supported. Possibly the
buffer_typevalue is invalid or is not one of the supported types.Out of memory.
An unknown error occurred.
The following example demonstrates binding one unnamed and one named parameter. The unnamed parameter hasNULL in a matching names array slot:.
// Compile example on Linux with a command similar to:// gcc example.c --std=c99 -I/usr/local/mysql/include -L/usr/local/mysql/lib -lmysqlclient -o example#include <mysql.h>#include <stdio.h>#include <stdlib.h>#include <string.h>int main(int argc, char *argv[]) { // variable declarations MYSQL *mysql; MYSQL_STMT *stmt; int int_data = 4; // unnamed input parameter value int int_parentid = 1329494394; // named ('traceparent') input parameter value MYSQL_BIND params[2]; const char *names[2] = {NULL, "traceparent"}; int rc; MYSQL_BIND rbind[1]; int result_val; // connect to the database server mysql = mysql_init(NULL); if (mysql == NULL) { fprintf(stderr, "%s\n", mysql_error(mysql)); return 1; } if (mysql_real_connect(mysql, "127.0.0.1", "root", "password", NULL, 0, NULL, 0) == NULL) { fprintf(stderr, "%s\n", mysql_error(mysql)); mysql_close(mysql); return 1; } // create a prepared statement stmt = mysql_stmt_init(mysql); if (stmt == NULL) { fprintf(stderr, "%s\n", mysql_error(mysql)); mysql_close(mysql); return 1; } const char *query = "SELECT POW(?,2) AS square"; if (mysql_stmt_prepare(stmt, query, strlen(query))) { mysql_stmt_close(stmt); mysql_close(mysql); return 1; } // bind the prepared statement parameters memset(params, 0, sizeof(params)); params[0].buffer_type = MYSQL_TYPE_LONG; params[0].buffer = (char *)&int_data; params[0].length = NULL; params[0].is_null = NULL; params[1].buffer_type = MYSQL_TYPE_LONG; params[1].buffer = (char *)&int_parentid; params[1].length = NULL; params[1].is_null = NULL; rc = mysql_stmt_bind_named_param(stmt, params, sizeof(params) / sizeof(params[0]), names); if (rc != 0) { fprintf(stderr, "%s\n", mysql_error(mysql)); mysql_stmt_close(stmt); mysql_close(mysql); return 1; } // execute the prepared statement rc = mysql_stmt_execute(stmt); if (rc != 0) { fprintf(stderr, "[%d] %s\n", mysql_stmt_errno(stmt), mysql_stmt_error(stmt)); mysql_stmt_close(stmt); mysql_close(mysql); return 1; } // bind and fetch the result parameter memset(rbind, 0, sizeof(rbind)); rbind[0].buffer_type = MYSQL_TYPE_LONG; rbind[0].buffer = (char *)&result_val; rc = mysql_stmt_bind_result(stmt, rbind); if (rc != 0) { fprintf(stderr, "[%d] %s\n", mysql_stmt_errno(stmt), mysql_stmt_error(stmt)); mysql_stmt_close(stmt); mysql_close(mysql); return 1; } rc = mysql_stmt_fetch(stmt); if (rc != 0) { fprintf(stderr, "[%d] %s\n", mysql_stmt_errno(stmt), mysql_stmt_error(stmt)); mysql_stmt_close(stmt); mysql_close(mysql); return 1; } // expect POW(4, 2), i.e. 4 squared being 16 if (result_val != 16) { printf("Unexpected result!\n"); } else { printf("Success!\n"); } mysql_stmt_close(stmt); mysql_close(mysql); return 0;}After executing, binding the results, and fetching data, the result of the statement on success is 16 (that is, 4 squared).
Seemysql_stmt_send_long_data() for sending long text or blob data in pieces. Refer to the filetests/mysql_client_test.c for complete examples. This file can be obtained from a MySQL source distribution or from the source repository (seeInstalling MySQL from Source).