General MySQL Oracle SQL Server

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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, 2258🔥, 0💬

Delete a Column in an Existing Table in Oracle
How To Delete a Column in an Existing Table in Oracle? If you have an existing column in a table and you need that column any more, you can delete it with ALTER TABLE ... DROP COLUMN statement. Here is an example SQL script: SQL&gt; CREATE TABLE emp_dept_90 2 AS SELECT * FROM employees WHERE dep... 2019-05-25, 2762🔥, 0💬

Add a New Column to an Existing Table with a Default Value in Oracle
How To Add a New Column to an Existing Table with a Default Value in Oracle? If you want to add a new column to an existing table, and insert a default value in this column on all existing data rows, you can use the ALTER TABLE ... ADD statement with the DEFAULT clause. Here is an example script: SQ... 2019-05-25, 2612🔥, 0💬

Rename a Column in an Existing Table in Oracle
How To Rename a Column in an Existing Table in Oracle? Let's say you have an existing with an existing column, but you don't like the name of that column, can you rename that column name? The answer is yes. You can use the ALTER TABLE ... RENAME COLUMN statement to do this. See the following SQL scr... 2019-05-25, 2384🔥, 0💬

Add a New Column to an Existing Table in Oracle
How To Add a New Column to an Existing Table in Oracle? If you have an existing table with existing data rows, and want to add a new column to that table, you can use the ALTER TABLE ... ADD statement to do this. Here is an example script: SQL&gt; connect HR/fyicenter Connected. SQL&gt; CREA... 2019-05-25, 2371🔥, 0💬

Drop an Existing Table 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... 2019-05-25, 2317🔥, 0💬

Show Dropped Tables in Recycle Bin in Oracle
How To View the Dropped Tables in Your Recycle Bin in Oracle? You can look what's in your recycle bin through the predefined view called RECYCLEBIN. You can use the SELECT statement to list the dropped tables as shown in the following script: SQL&gt; connect HR/fyicenter Connected. SQL&gt; C... 2019-05-14, 2624🔥, 0💬

Show All Columns in an Existing Table in Oracle
How To View All Columns in an Existing Table in Oracle? If you have an existing table and want to know how many columns are in the table and how they are defined, you can use the system view USER_TAB_COLUMNS as shown in the following tutorial exercise: SQL&gt; COL data_type FORMAT A12; SQL&g... 2019-05-14, 2540🔥, 0💬

Recycle Bin - Storage to Hold Dropped Tables in Oracle
What Is Recycle Bin in Oracle? Recycle bin is a logical storage to hold the tables that have been dropped from the database, in case it was dropped in error. Tables in recycle bin can be recovered back into database by the Flashback Drop action. Oracle database recycle save the same purpose as the r... 2019-05-14, 2349🔥, 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, 2274🔥, 0💬

Turn On and Off Recycle Bin for the Instance in Oracle
How To Turn On or Off Recycle Bin for the Instance in Oracle? You can turn on or off the recycle bin feature for an instance in the instance parameter file with "recyclebin=on/off". You can also turn on or off the recycle bin feature on the running instance with a SQL*Plus command, if you log in as ... 2019-05-14, 2207🔥, 0💬

Turn On and Off Recycle Bin for the Session in Oracle
How To Turn On or Off Recycle Bin for the Session in Oracle? If you want to control the recycle bin feature in your own session, you can use the ALTER SESSION statement to turn on or off. Here is an example SQL script: SQL&gt; connect HR/fyicenter Connected. SQL&gt; SELECT COUNT(*) FROM recy... 2019-05-10, 2465🔥, 0💬

Show All Tables in Your Schema in Oracle
How To List All Tables in Your Schema in Oracle? If you log in with your Oracle account, and you want to get a list of all tables in your schema, you can get it through the USER_TABLES view with a SELECT statement, as shown in the following SQL script: SQL&gt; connect HR/fyicenter Connected. SQL... 2019-05-10, 2394🔥, 0💬

Managing Oracle Table Indexes
Where to find answers to frequently asked questions on Managing Oracle Table Indexes? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Managing Oracle Table Indexes. The clear answers and sample scripts provided can be used as learning tutorials or... 2019-05-10, 2387🔥, 0💬

Empty Your Recycle Bin in Oracle
How To Empty Your Recycle Bin in Oracle? If your recycle bin is full, or you just want to clean your recycle bin to get rid of all the dropped tables, you can empty it by using the PURGE statement in two formats: PURGE RECYCLEBIN - Removes all dropped tables from your recycle bin. PURGE TABLE table_... 2019-05-10, 2372🔥, 0💬

Index - Data Structure for Query Performance in Oracle
What Is an Index in Oracle? Index is an optional structure associated with a table that allow SQL statements to execute more quickly against a table. Just as the index in this manual helps you locate information faster than if there were no index, an Oracle Database index provides a faster access pa... 2019-05-10, 2135🔥, 0💬

Indexes for the PRIMARY KEY Column in Oracle
What Is an Index Associated with a Constraint in Oracle? An index associated with a constraint because this constraint is required to have an index. There are two types of constraints are required to have indexes: UNIQUE and PRIMARY KEY. When you defines a UNIQUE or PRIMARY KEY constraint in a table... 2019-05-01, 2918🔥, 0💬

Run SQL Statement through Web UI in Oracle
How To Run SQL Statements through the Web Interface in Oracle? If you don't like the command line interface offered by SQL*Plus, you can use the Web interface to run SQL statements. Here is how: Open your Web browser to http://localhost:8080/apex/ Log in to the server with the predefined sample user... 2019-05-01, 2630🔥, 0💬

Rename an Index in Oracle
How To Rename an Index in Oracle? Let's say you have an existing index, and you don't like its name anymore for some reason, you can rename it with the ALTER INDEX ... RENAME TO statement. Here is an example script on how to rename an index: CREATE TABLE student (id NUMBER(5) PRIMARY KEY, first_name... 2019-05-01, 2438🔥, 0💬

Show All Indexes in Your Schema in Oracle
How To List All Indexes in Your Schema in Oracle? If you log in with your Oracle account, and you want to get a list of all indexes in your schema, you can get it through the USER_INDEXES view with a SELECT statement, as shown in the following SQL script: SELECT index_name, table_name, uniqueness FR... 2019-05-01, 2393🔥, 0💬

Create a Table Index in Oracle
How To Create a Table Index in Oracle? If you have a table with a lots of rows, and you know that one of the columns will be used often a search criteria, you can add an index for that column to in improve the search performance. To add an index, you can use the CREATE INDEX statement as shown in th... 2019-05-01, 2248🔥, 0💬

Recover a Dropped Index in Oracle
How To Recover a Dropped Index in Oracle? If you have the recycle bin feature turned on, dropped indexes are stored in the recycle bin. But it seems to be command to restore a dropped index out of the recycle bin. FLASHBACK INDEX is not a valid statement. See the following script: ALTER SESSION SET ... 2019-04-22, 5517🔥, 0💬

Drop an Index in Oracle
How To Drop an 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 NOT NULL, ... 2019-04-22, 4631🔥, 0💬

Dropped Tables with Indexes in Oracle
What Happens to Indexes If You Drop a Table in Oracle? If you drop a table, what happens to its indexes? The answer is that if a table is dropped, all its indexes will be dropped too. Try the following script to see yourself: CREATE TABLE student (id NUMBER(5) PRIMARY KEY, first_name VARCHAR(80) NOT... 2019-04-22, 2751🔥, 0💬

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General MySQL Oracle SQL Server