General MySQL Oracle SQL Server

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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, 500👍, 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, 602👍, 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, 560👍, 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, 528👍, 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, 510👍, 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, 491👍, 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, 672👍, 0💬

Recovered Tables with Indexes in Oracle
What Happens to the Indexes If a Table Is Recovered in Oracle? If you dropped a table, and recovered it back from the recycle bin, what happens to its indexes? Are all indexes recovered back automatically? The answer is that all indexes will be recovered, if you recover a dropped table from the recy... 2019-04-22, 574👍, 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, 547👍, 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, 545👍, 0💬

Error: Cannot Drop Index on Primary Key in Oracle
Can You Drop an Index Associated with a Unique or Primary Key Constraint in Oracle? You can not delete the index associated with a unique or primary key constraint. If you try, you will get an error like this: ORA-02429: cannot drop index used for enforcement of unique/primary key.   ⇒Managing Oracl... 2019-04-22, 485👍, 0💬

Managing Oracle Tablespaces and Data Files
Where to find answers to frequently asked questions on Managing Oracle Tablespaces and Data Files? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Managing Oracle Tablespaces and Data Files. Clear answers are provided with tutorial exercises on cr... 2019-04-17, 666👍, 0💬

Oracle Tablespace - Unit of Logical Storage in Oracle
What Is an Oracle Tablespace in Oracle? An Oracle tablespace is a big unit of logical storage in an Oracle database. It is managed and used by the Oracle server to store structures data objects, like tables and indexes.   ⇒Managing Oracle Tablespaces and Data Files ⇒⇒Oracle Database Tutorials 2019-04-17, 549👍, 0💬

Rebuild an Index in Oracle
How To Rebuild an Index in Oracle? If you want to rebuild an index, you can use the "ALTER INDEX ... REBUILD statement as shown in the following SQL script: SELECT index_name, table_name, uniqueness FROM USER_INDEXES WHERE table_name = 'EMPLOYEES'; INDEX_NAME TABLE_NAME UNIQUENES -------------------... 2019-04-17, 492👍, 0💬

Show Table Columns Used in an Index in Oracle
How To See the Table Columns Used in an Index in Oracle? You can a list of indexes in your schema from the USER_INDEXES view, but it will not give you the columns used in each index in the USER_INDEXES view. If you want to see the columns used in an index, you can use the USER_IND_COLUMNS view. Here... 2019-04-17, 473👍, 0💬

Create a Single Index for Multiple Columns in Oracle
How To Create a Single Index for Multiple Columns in Oracle? If you know a group of multiple columns will be always used together as search criteria, you should create a single index for that group of columns with the "ON table_name(col1, col2, ...)" clause. Here is an example of one index for two c... 2019-04-17, 437👍, 0💬

Show All Data Files in the Current Database in Oracle
How To View Data Files in the Current Database in Oracle? If you want to get a list of all tablespaces used in the current database instance, you can use the DBA_TABLESPACES view as shown in the following SQL script example: SQL&gt; connect SYSTEM/fyicenter Connected. SQL&gt; col tablespace_... 2019-04-13, 570👍, 0💬

Create a New Tablespace in Oracle
How To Create a New Tablespace in Oracle? If you want a new dataspace, you can use the CREATE TABLESPACE ... DATAFILE statement as shown in the following script: SQL&gt; CREATE TABLESPACE my_space 2 DATAFILE '/temp/my_space.dbf' SIZE 10M; Tablespace created. SQL&gt; SELECT TABLESPACE_NAME, S... 2019-04-13, 568👍, 0💬

Drop a Tablespace in Oracle
How To Drop a Tablespace in Oracle? If you have an existing tablespace and you don't want it anymore. You can delete a tablespace by using the DROP TABLESPACE statement as shown in the example below: SQL&gt; CREATE TABLESPACE my_space 2 DATAFILE '/temp/my_space.dbf' SIZE 10M; Tablespace created.... 2019-04-13, 552👍, 0💬

Rename a Tablespace in Oracle
How To Rename a Tablespace in Oracle? You can easily rename a tablespace by using the ALTER TABLESPACE ... RENAME TO statement as shown in the example below: SQL&gt; CREATE TABLESPACE my_space 2 DATAFILE '/temp/my_space.dbf' SIZE 10M; Tablespace created. SQL&gt; ALTER TABLESPACE my_space REN... 2019-04-13, 550👍, 0💬

Create a New Data File in Oracle
How To Create a New Oracle Data File in Oracle? There is no dedicated statement to create a data file. Data files are created as part of statements that manages other data structures, like tablespace and database.   ⇒Managing Oracle Tablespaces and Data Files ⇒⇒Oracle Database Tutorials 2019-04-13, 531👍, 0💬

Creating New Database Instance Manually
Where to find answers to frequently asked questions on Creating New Database Instance Manually? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on creating Oracle database instances manually using CREATE DATABASE statement. Items in this FAQ collecti... 2019-04-09, 622👍, 0💬

Add Another Datafile to a Tablespace in Oracle
How To Add Another Datafile to a Tablespace in Oracle? If you created a tablespace with a data file a month ago, now 80% of the data file is used, you should add another data file to the tablespace. This can be done by using the ALTER TABLESPACE ... ADD DATAFILE statement. See the following sample s... 2019-04-09, 611👍, 0💬

Remove Data Files before Opening a Database in Oracle
How Remove Data Files before Opening a Database in Oracle? Let's say you have a corrupted data file or lost a data file. Oracle can mount the database. But it will not open the database. What you can do is to set the bad data file as offline before opening the database. The tutorial exercise shows y... 2019-04-09, 551👍, 0💬

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General MySQL Oracle SQL Server