mirror of
https://github.com/yasuhirokimura/db18
synced 2026-06-08 18:29:23 +00:00
Yasuhiro KIMURA
105 lines
2.6 KiB
C
105 lines
2.6 KiB
C
/*-
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* Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
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*
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* See the file EXAMPLES-LICENSE for license information.
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*
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*/
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#include "ex_sql_utils.h"
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/*
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* Use sqlite3_prepare() and sqlite3_step() to query and iterate query result.
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*
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* To execute an SQL query, it must first be compiled into a byte-code program
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* using one of routines sqlite3_prepare*(). The sqlite3_exec() interface is a
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* wrapper around sqlite3_prepare_v2(), sqlite3_step(), and
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* sqlite3_finalize(), so it's much more effective to use sqlite3_prepare() to
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* prepare the statement for use many times over.
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*
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* The sqlite3_prepare_v2() and sqlite3_prepare16_v2() interfaces are
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* recommended for all new programs. The two older interfaces are retained
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* for backwards compatibility, but their use is discouraged.
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*
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* You also can use sqlite3_get_table() to fetch result into memory data
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* structure directly. But it is subject to the size of result set and
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* available memory of system.
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*/
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/* Iterate query result. */
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static void
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iterate_query_result(db, stmt)
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db_handle *db;
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sqlite3_stmt* stmt;
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{
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int i, k, ncols;
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int rc;
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for (i=0; ;i++) {
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rc = sqlite3_step(stmt);
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error_handler(db);
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if (rc == SQLITE_ROW) {
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ncols = sqlite3_column_count(stmt);
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for(k=0; k < ncols; k++) {
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printf("%s\t", sqlite3_column_text(stmt, k));
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}
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printf("\n");
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} else if (rc == SQLITE_DONE)
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break;
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}
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}
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/* Example body. */
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static int
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ex_sql_statment(db)
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db_handle *db;
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{
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sqlite3_stmt* stmt;
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const char* sql;
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/* Prepare the statement for use, many times over. */
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sql = "SELECT rank, name FROM university;";
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echo_info(sql);
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sqlite3_prepare_v2(db, sql, (int)strlen(sql), &stmt, NULL);
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error_handler(db);
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echo_info("a. Iterate query result with prepared statement");
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iterate_query_result(db, stmt);
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/* We can reset the statment and use it again for many times.
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* The sqlite3_reset() function is called to reset a prepared
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* statement object back to its initial state, ready to be
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* re-executed. Any SQL statement variables that had values
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* bound to them using the sqlite3_bind_*() API retain their values.
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*/
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echo_info("b. Reset the statement and iterate query result again");
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sqlite3_reset(stmt);
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error_handler(db);
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iterate_query_result(db, stmt);
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/* Final cleanup. */
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sqlite3_finalize(stmt);
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error_handler(db);
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return 0;
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}
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int
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main()
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{
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db_handle *db;
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/* Setup environment and preload data. */
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db = setup("./ex_sql_statement.db");
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load_table_from_file(db, university_sample_data, 1/* Silent */);
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/* Run example. */
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ex_sql_statment(db);
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/* End. */
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cleanup(db);
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return 0;
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}
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