General MySQL Oracle SQL Server

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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, 2930🔥, 0💬

PL/SQL Functions in Oracle
What Is a Function in Oracle? A function is a named program unit. It consists of three parts: Declaration Part - Defining the function name, calling parameters, return value type, local variables and local procedures. Declaration part is required. Execution Part - Defining execution logic with execu... 2018-11-29, 2928🔥, 0💬

Create a New User Account in Oracle
How To Create a New User Account in Oracle? If you want to create a new user account, you can log in as SYSTEM and use the CREATE USER command as shown in the following example: &gt;.\bin\sqlplus /nolog SQL&gt; connect SYSTEM/fyicenter Connected. SQL&gt; CREATE USER DEV IDENTIFIED BY dev... 2019-07-21, 2926🔥, 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, 2926🔥, 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, 2923🔥, 0💬

Use "OUT" Parameters in Oracle
How To Use "OUT" Parameter Properly in Oracle? Here are the rules about OUT parameters: A formal OUT parameter acts like an un-initialized variable. It must be assigned with new values before the end of the procedure or function. An actual OUT parameter must be a variable. An actual OUT parameter wi... 2018-10-19, 2923🔥, 0💬

Scope of Local Variables in Oracle
What Is the Scope of a Local Variable in Oracle? The scope of a variable can be described with these rules: A variable is valid within the procedure or function where it is defined. A variable is also valid inside a sub procedure or function defined. If a variable name is collided with another varia... 2018-10-13, 2923🔥, 0💬

Set a READ ONLY Transaction in Oracle
How To Set a Transaction To Be READ ONLY in Oracle? If you want a transaction to be set as READ ONLY, you need to the transaction with the SET TRANSACTION READ ONLY statement. Note that a DML statement will start the transaction automatically. So you have to issue the SET TRANSACTION statement befor... 2019-08-19, 2920🔥, 0💬

SGA Setting Is Too Low in Oracle
What Happens If You Set the SGA Too Low in Oracle? Let's you made a mistake and changed to SGA to 16MB from the SYSTEM admin home page. When you run the batch file StartDB.bat, it will return a message saying server stated. However, if you try to connect to your server home page: http://localhost:80... 2020-09-30, 2919🔥, 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, 2919🔥, 0💬

Define Anonymous Procedures without Variables in Oracle
How To Define an Anonymous Procedure without Variables in Oracle? Anonymous procedure is a procedure without any name. If you don't have any variables to declare, you can define an anonymous procedure by using the BEGIN keyword directly in SQL*Plus as shown in the following tutorial script: SQL&... 2018-01-27, 2916🔥, 0💬

Working with Database Objects in Oracle PL/SQL
Where to find answers to frequently asked questions on Working with Database Objects in Oracle PL/SQL? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Working with Database Objects in Oracle PL/SQL. Clear answers are provided with tutorial exercis... 2018-10-13, 2914🔥, 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, 2909🔥, 0💬

Call a Sub Procedure in Oracle
How To Call a Sub Procedure in Oracle? To call a sub procedure, just use the sub procedure name as a statement. Here is another example of calling a sub procedure: SQL&gt; CREATE OR REPLACE PROCEDURE WELCOME AS 2 PROCEDURE WELCOME_PRINT(S CHAR) AS 3 BEGIN 4 DBMS_OUTPUT.PUT_LINE('Welcome to ' || ... 2018-10-26, 2908🔥, 0💬

Counting Groups Returned with the GROUP BY Clause in Oracle
How To Count Groups Returned with the GROUP BY Clause in Oracle? If you use the COUNT(*) function on groups returned with the GROUP BY clause, it will count the number of rows within each group, not the number of groups. If you want to count the number of groups, you can put the GROUP BY query into ... 2019-09-16, 2905🔥, 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.   ⇒ Oracle Data File - Unit of Physical Storage in Oracle ⇐ Managing Oracle Tab... 2019-04-17, 2905🔥, 0💬

Left Outer Join with the WHERE Clause in Oracle
How To Write a Left Outer Join with the WHERE Clause in Oracle? If you don't want to use the LEFT OUTER JOIN ... ON clause to write a left outer join, you can use a special criteria in the WHERE clause as "left_table.column = right_table.column(+)". The select statement below is an example of a left... 2019-10-18, 2901🔥, 0💬

Use Values from Other Tables in UPDATE in Oracle
How To Use Values from Other Tables in UPDATE Statements in Oracle? If you want to update values in one with values from another table, you can use a subquery in the SET clause. The subquery should return only one row for each row in the update table that matches the WHERE clause. The tutorial exerc... 2020-01-21, 2898🔥, 0💬

Rename an Existing Table in Oracle
How To Rename an Existing Table in Oracle? If you don't like the name of an existing table, you change it by using the CREATE TABLE ... RENAME TO statement. Here is a sample script: SQL&gt; connect HR/fyicenter Connected. SQL&gt; CREATE TABLE emp_dept_10 2 AS SELECT * FROM employees WHERE de... 2019-06-01, 2898🔥, 0💬

Restrictions in a READ ONLY Transaction in Oracle
What Are the Restrictions in a READ ONLY Transaction in Oracle? There are lots of restrictions in a READ ONLY transaction: You can not switch to READ WRITE mode. You can not run any INSERT, UPDATE, DELETE statements. You can run SELECT query statements. The tutorial exercise below shows you some of ... 2019-08-19, 2892🔥, 0💬

Execute a Simple Stored Procedure in Oracle
How To Execute a Stored Program Unit in Oracle? If you want to execute a stored program unit, you can use the EXECUTE statement. The example script below shows how to executes a stored program unit: SQL&gt; set serveroutput on; SQL&gt; CREATE PROCEDURE Hello AS 2 BEGIN 3 DBMS_OUTPUT.PUT_LINE... 2019-03-20, 2891🔥, 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, 2889🔥, 0💬

Arithmetic Operations in Pl/SQL in Oracle
What Are the Arithmetic Operations in Oracle? There are 4 basic arithmetic operations on numeric values as shown in the following sample script: PROCEDURE proc_arithmetic AS addition NUMBER; subtraction NUMBER; multiplication NUMBER; division NUMBER; BEGIN addition := 7 + 8; subtraction := addition ... 2018-08-06, 2889🔥, 0💬

Show Execution Path Reports in Oracle
How To Get Execution Path Reports on Query Statements in Oracle? If your user account has autotrace configured by the DBA, you can use the "SET AUTOTRACE ON EXPLAIN" command to turn on execution path reports on query statements. The tutorial exercise bellow shows you a good example: SQL&gt; CONN... 2020-06-08, 2885🔥, 0💬

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General MySQL Oracle SQL Server