mirror of
https://github.com/taosdata/TDengine
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8bd3ea1ef4
* docs: add taos_print_row desc * docs: update query examples * docs: update tmq and query examples * docs: update c docs * docs: modify comment info
77 lines
2.2 KiB
C
77 lines
2.2 KiB
C
// to compile: gcc -o query_data_demo query_data_demo.c -ltaos
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#include <inttypes.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "taos.h"
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static int DemoQueryData() {
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// ANCHOR: query_data
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const char *host = "localhost";
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const char *user = "root";
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const char *password = "taosdata";
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uint16_t port = 6041;
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int code = 0;
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code = taos_options(TSDB_OPTION_DRIVER, "websocket");
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if (code != 0) {
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fprintf(stderr, "Failed to set driver option, code: %d\n", code);
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return -1;
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}
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// connect
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TAOS *taos = taos_connect(host, user, password, NULL, port);
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if (taos == NULL) {
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fprintf(stderr, "Failed to connect to %s:%hu, ErrCode: 0x%x, ErrMessage: %s.\n", host, port, taos_errno(NULL),
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taos_errstr(NULL));
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taos_cleanup();
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return -1;
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}
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// query data, please make sure the database and table are already created
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const char *sql = "SELECT ts, current, location FROM power.meters limit 100";
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TAOS_RES *result = taos_query(taos, sql);
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code = taos_errno(result);
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if (code != 0) {
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fprintf(stderr, "Failed to query data from power.meters, sql: %s, ErrCode: 0x%x, ErrMessage: %s\n.", sql, code,
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taos_errstr(result));
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taos_close(taos);
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taos_cleanup();
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return -1;
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}
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TAOS_ROW row = NULL;
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int rows = 0;
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char buffer[1024];
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int num_fields = taos_num_fields(result);
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TAOS_FIELD *fields = taos_fetch_fields(result);
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fprintf(stdout, "query successfully, got %d fields, the sql is: %s.\n", num_fields, sql);
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// fetch the records row by row
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while ((row = taos_fetch_row(result))) {
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// Add your data processing logic here
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rows++;
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// Print the data for easy debugging. You can uncomment them if needed.
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// code = taos_print_row(buffer, row, fields, num_fields);
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// if (code > 0) {
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// fprintf(stdout, "row %d: %s\n", rows, buffer);
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// } else {
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// fprintf(stderr, "Failed to print row %d data, ErrCode: 0x%x, ErrMessage: %s\n", rows, taos_errno(NULL),
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// taos_errstr(NULL));
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// }
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}
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fprintf(stdout, "total rows: %d\n", rows);
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taos_free_result(result);
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// close & clean
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taos_close(taos);
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taos_cleanup();
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return 0;
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// ANCHOR_END: query_data
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}
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int main() { return DemoQueryData(); }
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