[add prepare demo file]

tests/examples/c/prepare.c

+// TAOS standard API example. The same syntax as MySQL, but only a subet 
+// to compile: gcc -o prepare prepare.c -ltaos
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "taos.h"
+
+
+void taosMsleep(int mseconds);
+
+int main(int argc, char *argv[])
+{
+  TAOS     *taos;
+  TAOS_RES *result;
+  TAOS_STMT *stmt;
+
+  // connect to server
+  if (argc < 2) {
+    printf("please input server ip \n");
+    return 0;
+  }
+
+  // init TAOS
+  taos_init();
+
+  taos = taos_connect(argv[1], "root", "taosdata", NULL, 0);
+  if (taos == NULL) {
+    printf("failed to connect to db, reason:%s\n", taos_errstr(taos));
+    exit(1);
+  }
+
+  taos_query(taos, "drop database demo");
+  if (taos_query(taos, "create database demo") != 0) {
+    printf("failed to create database, reason:%s\n", taos_errstr(taos));
+    exit(1);
+  }
+
+  taos_query(taos, "use demo");
+
+
+  // create table
+  const char* sql = "create table m1 (ts timestamp, b bool, v1 tinyint, v2 smallint, v4 int, v8 bigint, f4 float, f8 double, bin binary(40), blob nchar(10))";
+  if (taos_query(taos, sql) != 0) {
+    printf("failed to create table, reason:%s\n", taos_errstr(taos));
+    exit(1);
+  }
+
+  // sleep for one second to make sure table is created on data node
+  // taosMsleep(1000);
+
+  // insert 10 records
+  struct {
+      int64_t ts;
+      int8_t b;
+      int8_t v1;
+      int16_t v2;
+      int32_t v4;
+      int64_t v8;
+      float f4;
+      double f8;
+      char bin[40];
+      char blob[80];
+  } v = {0};
+
+  stmt = taos_stmt_init(taos);
+  TAOS_BIND params[10];
+  params[0].buffer_type = TSDB_DATA_TYPE_TIMESTAMP;
+  params[0].buffer_length = sizeof(v.ts);
+  params[0].buffer = &v.ts;
+  params[0].length = &params[0].buffer_length;
+  params[0].is_null = NULL;
+
+  params[1].buffer_type = TSDB_DATA_TYPE_BOOL;
+  params[1].buffer_length = sizeof(v.b);
+  params[1].buffer = &v.b;
+  params[1].length = &params[1].buffer_length;
+  params[1].is_null = NULL;
+
+  params[2].buffer_type = TSDB_DATA_TYPE_TINYINT;
+  params[2].buffer_length = sizeof(v.v1);
+  params[2].buffer = &v.v1;
+  params[2].length = &params[2].buffer_length;
+  params[2].is_null = NULL;
+
+  params[3].buffer_type = TSDB_DATA_TYPE_SMALLINT;
+  params[3].buffer_length = sizeof(v.v2);
+  params[3].buffer = &v.v2;
+  params[3].length = &params[3].buffer_length;
+  params[3].is_null = NULL;
+
+  params[4].buffer_type = TSDB_DATA_TYPE_INT;
+  params[4].buffer_length = sizeof(v.v4);
+  params[4].buffer = &v.v4;
+  params[4].length = &params[4].buffer_length;
+  params[4].is_null = NULL;
+
+  params[5].buffer_type = TSDB_DATA_TYPE_BIGINT;
+  params[5].buffer_length = sizeof(v.v8);
+  params[5].buffer = &v.v8;
+  params[5].length = &params[5].buffer_length;
+  params[5].is_null = NULL;
+
+  params[6].buffer_type = TSDB_DATA_TYPE_FLOAT;
+  params[6].buffer_length = sizeof(v.f4);
+  params[6].buffer = &v.f4;
+  params[6].length = &params[6].buffer_length;
+  params[6].is_null = NULL;
+
+  params[7].buffer_type = TSDB_DATA_TYPE_DOUBLE;
+  params[7].buffer_length = sizeof(v.f8);
+  params[7].buffer = &v.f8;
+  params[7].length = &params[7].buffer_length;
+  params[7].is_null = NULL;
+
+  params[8].buffer_type = TSDB_DATA_TYPE_BINARY;
+  params[8].buffer_length = sizeof(v.bin);
+  params[8].buffer = v.bin;
+  params[8].length = &params[8].buffer_length;
+  params[8].is_null = NULL;
+
+  strcpy(v.blob, "一二三四五六七八九十");
+  params[9].buffer_type = TSDB_DATA_TYPE_NCHAR;
+  params[9].buffer_length = strlen(v.blob);
+  params[9].buffer = v.blob;
+  params[9].length = &params[9].buffer_length;
+  params[9].is_null = NULL;
+
+  int is_null = 1;
+
+  sql = "insert into m1 values(?,?,?,?,?,?,?,?,?,?)";
+  int code = taos_stmt_prepare(stmt, sql, 0);
+  if (code != 0){
+    printf("failed to execute taos_stmt_prepare. code:0x%x\n", code);
+  }
+  v.ts = 1591060628000;
+  for (int i = 0; i < 10; ++i) {
+    v.ts += 1;
+    for (int j = 1; j < 10; ++j) {
+      params[j].is_null = ((i == j) ? &is_null : 0);
+    }
+    v.b = (int8_t)i % 2;
+    v.v1 = (int8_t)i;
+    v.v2 = (int16_t)(i * 2);
+    v.v4 = (int32_t)(i * 4);
+    v.v8 = (int64_t)(i * 8);
+    v.f4 = (float)(i * 40);
+    v.f8 = (double)(i * 80);
+    for (int j = 0; j < sizeof(v.bin) - 1; ++j) {
+      v.bin[j] = (char)(i + '0');
+    }
+
+    taos_stmt_bind_param(stmt, params);
+    taos_stmt_add_batch(stmt);
+  }
+  if (taos_stmt_execute(stmt) != 0) {
+    printf("failed to execute insert statement.\n");
+    exit(1);
+  }
+  taos_stmt_close(stmt);
+  printf("==== success inset data ====.\n");
+
+  // query the records
+  stmt = taos_stmt_init(taos);
+  taos_stmt_prepare(stmt, "SELECT * FROM m1 WHERE v1 > ? AND v2 < ?", 0);
+  v.v1 = 5;
+  v.v2 = 15;
+  taos_stmt_bind_param(stmt, params + 2);
+  if (taos_stmt_execute(stmt) != 0) {
+    printf("failed to execute select statement.\n");
+    exit(1);
+  }
+
+  result = taos_stmt_use_result(stmt);
+
+  TAOS_ROW    row;
+  int         rows = 0;
+  int         num_fields = taos_num_fields(result);
+  TAOS_FIELD *fields = taos_fetch_fields(result);
+  char        temp[256];
+
+  // fetch the records row by row
+  while ((row = taos_fetch_row(result))) {
+    rows++;
+    taos_print_row(temp, row, fields, num_fields);
+    printf("%s\n", temp);
+  }
+
+  taos_free_result(result);
+  taos_stmt_close(stmt);
+
+  return getchar();
+}
+