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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1997, 2015 Oracle and/or its affiliates. All rights reserved.
*
*/
#include "ex_sql_utils.h"
/*
* This example demonstrates the use of indexes.
* Step 1. Explain a query and output the query plan
* Step 2. Create an index
* Step 3. Explain above query again to see how query plan is simplified
* Step 4. Drop the index
*/
/* Example body. */
static int
ex_sql_index(db)
db_handle *db;
{
const char* sql_1;
const char* sql_2;
/*
* Explain a query expression to get the query plan.
*/
echo_info("STEP1. Explain a query expression");
sql_1 = "\tEXPLAIN \n"
"\tSELECT rank, country, name \n"
"\tfrom university \n"
"\tWHERE region = 'Europe' \n"
"\tORDER BY country;";
exec_sql(db, sql_1);
/*
* Now create index.
*/
echo_info("STEP2. Create an index on university(region, country)");
sql_2 = "\tCREATE INDEX university_geo \n"
"\tON university (region, country);";
exec_sql(db, sql_2);
/*
* Now we check query plan again. We can see reasonable indexes
* can simplify query plan.
*/
echo_info("STEP3. Explain the query again, we can see the difference");
exec_sql(db, sql_1);
/*
* Drop the index.
*/
echo_info("STEP4. Drop the index");
sql_2 = "DROP INDEX university_geo;";
exec_sql(db, sql_2);
return 0;
}
int
main()
{
db_handle *db;
/* Setup environment and preload data. */
db = setup("./ex_sql_index.db");
load_table_from_file(db, university_sample_data, 1/* Silent */);
/* Run example. */
ex_sql_index(db);
/* End. */
cleanup(db);
return 0;
}
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