General MySQL Oracle SQL Server

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Create an Oracle Database Manually in Oracle
How To Create an Oracle Database Manually in Oracle? Based on Oracle's Administrator Guide, there are 11 steps to create a database with the CREATE DATABASE statement: Step 1: Decide on Your Instance Identifier (SID) Step 2: Establish the Database Administrator Authentication Method Step 3: Create t... 2019-04-03, 2438🔥, 0💬

Query with a Right Outer Join in Oracle
How To Write a Query with a Right Outer Join in Oracle? If you want to query from two tables with a right outer join, you can use the RIGHT OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a right outer join from two tables: departments and employees. The join con... 2019-10-18, 2436🔥, 0💬

What Is a SELECT Query Statement in Oracle
What Is a SELECT Query Statement in Oracle? The SELECT statement is also called the query statement. It is the most frequently used SQL statement in any database application. A SELECT statement allows you to retrieve data from one or more tables, or views, with different selection criteria, grouping... 2020-01-04, 2434🔥, 0💬

Restrictions on External Table Columns in Oracle
What Are the Restrictions on External Table Columns in Oracle? When creating external table columns, you need to watch out some restrictions: "PRIMARY KEY" is not allowed. "NOT NULL" is not allowed. "DEFAULT value" is not allowed.   ⇒ What Is a Directory Object in Oracle ⇐ Load Data through Externa... 2016-11-27, 2432🔥, 0💬

DROP TABLE Statement in Oracle
How To Drop an Existing Table in Oracle? If you want to delete an existing table and its data rows, you can use the DROP TABLE statement as shown in this script: SQL&gt; connect HR/fyicenter Connected. SQL&gt; CREATE TABLE emp_dept_10 2 AS SELECT * FROM employees WHERE department_id=10; Tabl... 2020-02-20, 2431🔥, 0💬

What Is a Transaction in Oracle
What Is a Transaction in Oracle? A transaction is a logical unit of work requested by a user to be applied to the database objects. Oracle server introduces the transaction concept to allow users to group one or more SQL statements into a single transaction, so that the effects of all the SQL statem... 2019-09-16, 2428🔥, 0💬

Use DML Statements in PL/SQL in Oracle
Can DML Statements Be Used in PL/SQL in Oracle? Yes, you can run almost any DML statements in PL/SQL directly. To manipulate Oracle database data you can include INSERT, UPDATE, and DELETE statements, directly in PL/SQL programs, without any special notation, as shown in the following sample code: (... 2018-10-13, 2427🔥, 0💬

Convert Character Types to Numeric Types in Oracle
How To Convert Character Types to Numeric Types in Oracle? You can convert character types to numeric types in two ways: Explicitly by using TO_NUMBER() function. Implicitly by putting character data in a numeric operation. The sample script below shows you how to convert character types to numeric ... 2018-11-17, 2426🔥, 0💬

Rollback the Current Transaction in Oracle
How To Rollback the Current Transaction in Oracle? If you have used some DML statements updated some data objects, you find a problem with those updates, and you don't want those updates to be permanently recorded in the database, you can use the ROLLBACK statement. It will remove all the database c... 2019-09-04, 2424🔥, 0💬

Run SQL Statements with SQL Developer in Oracle
How To Run SQL Statements with Oracle SQL Developer in Oracle? Once a connection is established with an Oracle server, you can enter any SQL statements in the SQL Statement area. Try yourself with the following steps: Go to the SQL Statement area Enter SELECT username, default_tablespace FROM USER_U... 2018-10-08, 2423🔥, 0💬

Recover a Dropped Table in Oracle
How To Recover a Dropped Table in Oracle? If you accidentally dropped a table, can you recover it back? The answer is yes, if you have the recycle bin feature turned on. You can use the FLASHBACK TABLE ... TO BEFORE DROP statement to recover a dropped table from the recycle bin as shown in the follo... 2019-05-14, 2419🔥, 0💬

Update a Table Row with a RECORD in Oracle
How To Update a Table Row with a RECORD in Oracle? If you have a RECORD variable with data fields matching a table structure, you can update a row in this table with this RECORD variable using the UPDATE ... SET ROW statement as shown in the sample script below: CREATE TABLE emp_temp AS SELECT * FRO... 2018-08-14, 2419🔥, 0💬

Show Existing Locks on the Database in Oracle
How To View Existing Locks on the Database in Oracle? As can see from the pervious tutorial exercise, performance of the second session is greatly affected by the data lock created on the database. To maintain a good performance level for all sessions, you need to monitor the number of data locks on... 2019-08-08, 2418🔥, 0💬

Loop through a Cursor Variable in Oracle
How To Loop through a Cursor Variable in Oracle? Once a cursor variable is opened with a query statement, it will have the same attributes as a normal cursor and it can be used in the same way a normal cursor too. The following sample script shows you how to loop through a cursor variable: CREATE OR... 2018-07-18, 2416🔥, 0💬

Create a Stored Procedure Interactively in Oracle
How To Create a Procedure Interactively in Oracle? If you want to create a stored procedure interactively, you can use the following steps: Open you connection name, like Local_XE. Right-click Procedures. Select Create PROCEDURE. The Create Procedure window shows up. Enter Name as: Hello Click OK. T... 2019-01-12, 2415🔥, 0💬

Insert a RECORD into a Table in Oracle
How To Insert a RECORD into a Table in Oracle? If you have a RECORD variable with data fields matching a table structure, you can insert a row to this table with this RECORD variable using the INSERT statement as shown in the example below: CREATE TABLE emp_temp AS SELECT * FROM employees; CREATE OR... 2018-08-14, 2415🔥, 0💬

General Rules on Data Consistency in Oracle
What Are the General Rules on Data Consistency in Oracle? Here is a list of general rules on data consistency: All SQL statements always work with a snapshot of the database to provide data consistency. For READ WRITE transactions, the snapshot is taken when each statement starts. For READ ONLY tran... 2019-08-19, 2414🔥, 0💬

Drop an Existing Index in Oracle
How To Drop an Existing Index in Oracle? If you don't need an existing index any more, you should delete it with the DROP INDEX statement. Here is an example SQL script: CREATE TABLE student (id NUMBER(5) PRIMARY KEY, first_name VARCHAR(80) NOT NULL, last_name VARCHAR(80) NOT NULL, birth_date DATE N... 2020-02-20, 2413🔥, 0💬

Omit Columns in INSERT Statements in Oracle
How To Omit Columns with Default Values in INSERT Statement in Oracle? If you don't want to specify values for columns that have default values, or you want to specify values to columns in an order different than how they are defined, you can provide a column list in the INSERT statement. If a colum... 2020-01-29, 2411🔥, 0💬

Retrieve Data from an Explicit Cursor in Oracle
How To Retrieve Data from an Explicit Cursor in Oracle? If you have a cursor opened ready to use, you can use the FETCH ... INTO statement to retrieve data from the cursor into variables. FETCH statement will: Retrieve all the fields from the row pointed by the current cursor pointer and assign them... 2018-07-22, 2411🔥, 0💬

What Is Oracle Server Autotrace in Oracle
What Is Oracle Server Autotrace in Oracle? Autotrace is Oracle server feature that generates two statement execution reports very useful for performance tuning: Statement execution path - Shows you the execution loop logic of a DML statement. Statement execution statistics - Shows you various execut... 2020-06-08, 2410🔥, 0💬

Create a New Table by Selecting Rows from Another Table in Oracle
How To Create a New Table by Selecting Rows from Another Table in Oracle? Let's say you have a table with many data rows, now you want to create a backup copy of this table of all rows or a subset of them, you can use the CREATE TABLE...AS SELECT statement to do this. Here is an example script: &... 2019-06-01, 2410🔥, 0💬

Select All Columns of All Rows in Oracle
How To Select All Columns of All Rows from a Table in Oracle? The simplest query statement is the one that selects all columns of all rows from a table: "SELECT * FROM table_name;". The (*) in the SELECT clause tells the query to return all columns. The tutorial exercise below gives you a good examp... 2019-12-19, 2406🔥, 0💬

Drop an Existing View in Oracle
How To Drop an Existing View in Oracle? If you have an existing view, and you don't want it anymore, you can delete it by using the DROP VIEW statement as shown in the following script: DROP VIEW employee_department; View dropped.   ⇒ Understanding SQL DML Statements for Oracle ⇐ Create a New View ... 2020-02-07, 2404🔥, 0💬

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General MySQL Oracle SQL Server