Press CTRL+C to copybool mysql_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 old
mysql_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 inNULL
as 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 array MYSQL_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 is
NULL
. It fails if an invalid
MYSQL_BIND
type is used for any bind
parameter arguments.
To store both named and unnamed bind user variables, call
mysql_stmt_bind_named_param()
after mysql_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 the
MYSQL_STMT
and
MYSQL_BIND
structure and how they should be
set to provide input values, see
Section 6.2, “C API Prepared Statement Data Structures”.
-
The conversion is not supported. Possibly the
buffer_type
value 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 has
NULL
in a matching names array slot:.
Press CTRL+C to copy// 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).
See
mysql_stmt_send_long_data()
for sending long text or blob data in pieces. Refer to the
file tests/mysql_client_test.c
for
complete examples. This file can be obtained from a MySQL
source distribution or from the source repository (see
Installing MySQL from Source).