85 lines
3.0 KiB
JavaScript
85 lines
3.0 KiB
JavaScript
/* Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved. */
|
|
|
|
/******************************************************************************
|
|
*
|
|
* You may not use the identified files except in compliance with the Apache
|
|
* License, Version 2.0 (the "License.")
|
|
*
|
|
* You may obtain a copy of the License at
|
|
* http://www.apache.org/licenses/LICENSE-2.0.
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
*
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
* NAME
|
|
* rowlimit.js
|
|
*
|
|
* DESCRIPTION
|
|
* Shows ways to limit the number of records fetched by queries.
|
|
* Uses Oracle's sample HR schema.
|
|
*
|
|
* Scripts to create the HR schema can be found at:
|
|
* https://github.com/oracle/db-sample-schemas/releases
|
|
*
|
|
* Although adjusting maxRows can be used to control the number of
|
|
* rows available to the application, it is more efficient for the
|
|
* database if the SQL query syntax limits the number of rows
|
|
* returned from the database. Use maxRows only to prevent badly
|
|
* coded queries from over-consuming Node.js resources.
|
|
*
|
|
*****************************************************************************/
|
|
|
|
var oracledb = require('oracledb');
|
|
var dbConfig = require('./dbconfig.js');
|
|
|
|
var myoffset = 2; // number of rows to skip
|
|
var mymaxnumrows = 6; // number of rows to fetch
|
|
|
|
// Properties are applicable to all connections and SQL executions.
|
|
// They can also be set or overridden at the individual execute() call level
|
|
//
|
|
// This script sets maxRows in the execute() call but it could be set here instead
|
|
// oracledb.maxRows = 150; // Note the default value is 0, meaning unlimited
|
|
|
|
oracledb.getConnection(
|
|
{
|
|
user : dbConfig.user,
|
|
password : dbConfig.password,
|
|
connectString : dbConfig.connectString
|
|
},
|
|
function (err, connection) {
|
|
if (err) {
|
|
console.error(err.message);
|
|
return;
|
|
}
|
|
|
|
var sql = "SELECT employee_id, last_name FROM employees ORDER BY employee_id";
|
|
if (connection.oracleServerVersion >= 1201000000) {
|
|
// 12c row-limiting syntax
|
|
sql += " OFFSET :offset ROWS FETCH NEXT :maxnumrows ROWS ONLY";
|
|
} else {
|
|
// Pre-12c syntax [could also customize the original query and use row_number()]
|
|
sql = "SELECT * FROM (SELECT A.*, ROWNUM AS MY_RNUM FROM"
|
|
+ "(" + sql + ") A "
|
|
+ "WHERE ROWNUM <= :maxnumrows + :offset) WHERE MY_RNUM > :offset";
|
|
}
|
|
|
|
connection.execute(
|
|
sql,
|
|
{ offset: myoffset, maxnumrows: mymaxnumrows },
|
|
{ maxRows: 150 },
|
|
function(err, result) {
|
|
if (err) {
|
|
console.error(err.message);
|
|
} else {
|
|
console.log("Executed: " + sql);
|
|
console.log("Number of rows returned: " + result.rows.length);
|
|
console.log(result.rows);
|
|
}
|
|
});
|
|
});
|