Indexes. They're one of the most powerful and misunderstood aspects of SQL performance. In this post we'll look at the purpose of an index, how to create and choose choose your index type. Then finish with a di
The insert statement adds a new row or rows in a table in theOracle database. We generally use it after we have created a table in the database. One important point to remember is that while inserting records into a table, we must provide a value for every NOT NULL value. Let us lo...
Oracle SQL Developer is the database IDE and Oracle SQL Developer Data Modeler is our dedicated data modeling solution. Where it gets interesting is that the entire Data Modeler product also runs inside of SQL Developer. When I do demo’s of building quick ad hoc models in SQL Developer, ...
Perform the following actions to create a new database user: It should be noted that you can skip these steps if you already have a system orcl connection and a mwrep user. Step 1: Use the desktop icon to launch Oracle SQL Developer. Step 2: Select the Connections option under View. ...
Each set of values in its columns can only appear once. So you can't have duplicates. It also has a not null constraint. And creates a unique index in the background.To create one, add the organization index clause to the table definition:...
Updated: Nov 2009 for SQL Developer 2.1 1. Introduction Oracle SQL Developer provides a SQL Worksheet that you can use to update data, by writing simple or complex SQL statements. In this How-To, we look at the most basic of these, inserting a record, updating single and multiple records...
http://www.oracle.com/technology/obe/hol08/apexintro/apex3.1.1_c/apex3.1.1_c_otn.htm Creating an Application First, you need to create an application using the Create Application Wizard. To create an application using the Create Application Wizard: ...
MySQL derives part of its name from the SQL language, which is used for managing and querying data in databases. MySQL offers full ACID transactions and can handle a high volume of concurrent connections. MySQL Explained MySQL is an open source RDBMS that uses SQL to create and manage database...
query to find unique constraints on a table in oracle SQL> CREATE TABLE DEPT_MASTER ( dept_nr NUMBER UNIQUE, dept_name varchar2(100) NOT NULL, dept_status NUMBER(1,0) NOT NULL, created_at date ); Table created. SQL> select CONSTRAINT_NAME,INDEX_NAME,CONSTRAINT_TYPE from user_constraints...
Because a block device’s total size is fixed and easy to index, processes have random access to any block in the device with the help of the kernel. 程序以固定的块大小从块设备中访问数据。 上述示例中的sda1是一个磁盘设备,也是一种块设备。 磁盘可以被分割成数据块。 由于块设备的总大小是...