General MySQL Oracle SQL Server

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Select Some Columns from a Table in Oracle
How To Select Some Columns from a Table in Oracle? If you want explicitly tell the query to some columns, you can specify the column names in SELECT clause. The following select statement returns only two columns from the table "departments": SQL&gt; SELECT location_id, department_name FROM DEPA... 2019-12-19, 2581🔥, 0💬

Use Subqueries with the EXISTS Operator in Oracle
How To Use Subqueries with the EXISTS Operator in Oracle? A subquery can be used with the EXISTS operator as "EXISTS (subquery)", which returns true if the subquery returns one or more rows. The following statement is a good example of "EXISTS (subquery)". It returns rows from employees table that t... 2019-09-27, 2581🔥, 0💬

Convert Numbers to Character Strings in Oracle
How To Convert Numbers to Character Strings in Oracle? You can convert numeric values to characters by using the TO_CHAR() function as shown in the following examples: SELECT TO_CHAR(4123.4570) FROM DUAL 123.457 SELECT TO_CHAR(4123.457, '$9,999,999.99') FROM DUAL $4,123.46 SELECT TO_CHAR(-4123.457, ... 2020-03-25, 2579🔥, 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, 2579🔥, 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, 2577🔥, 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, 2574🔥, 0💬

Process Query Result in PL/SQL in Oracle
How To Process Query Result in PL/SQL in Oracle? You can run queries (SELECT statements) in a PL/SQL code blocks, and process the results a loop as shown in the following script example: SQL&gt; set serveroutput on; SQL&gt; BEGIN 2 FOR row IN 3 (SELECT * FROM employees WHERE manager_id = 101... 2019-03-08, 2572🔥, 0💬

File Formats Supported on Export Data in Oracle
How Many File Formats Are Supported to Export Data in Oracle? Oracle SQL Developer can allow to export table data into files in the following formats: TXT - Tab delimited fields file format. CSV - Comma Separated Values (CSV) file format. LOADER - File format used by SQL*Loader. XML - XML file forma... 2019-01-26, 2571🔥, 0💬

Export Several Tables Together in Oracle
How To Export Several Tables Together in Oracle? If you don't want to export the entire schema and only want to export several tables only, you can use the "expdp" command with the "TABLES" parameter as shown in the following tutorial exercise: &gt;cd \oraclexe\app\oracle\product\1 0.2.0\server\B... 2016-10-15, 2570🔥, 0💬

Define a Sub Procedure in Oracle
How To Define a Sub Procedure in Oracle? A sub procedure is a named procedure defined and used inside another procedure or function. You need to define a sub procedure in the declaration part of the enclosing procedure or function. Sub procedure definition starts with the PROCEDURE key word. Here is... 2018-10-26, 2567🔥, 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, 2566🔥, 0💬

How Oracle Handles Dead Locks in Oracle
How Oracle Handles Dead Locks in Oracle? Oracle server automatically detects dead locks. When a dead lock is detected, Oracle server will select a victim transaction, and fail its statement that is blocked in the dead lock to break the dead lock. The tutorial exercise below shows you an example of s... 2019-08-08, 2566🔥, 0💬

Show Installed Oracle ODBC Drivers in Oracle
How To Find Out What Oracle ODBC Drivers Are Installed in Oracle? To find out what Oracle ODBC drivers are installed on your Windows system, you can use the ODBC manager to look at them: Go to Control Panel. Go to Administrative Tools. Run Data Sources (ODBC). Go to System DSN tab. Click the Add but... 2016-10-15, 2566🔥, 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, 2564🔥, 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, 2564🔥, 0💬

Pass a Cursor Variable to a Procedure in Oracle
How To Pass a Cursor Variable to a Procedure in Oracle? A cursor variable can be passed into a procedure like a normal variable. The sample script below gives you a good example: CREATE OR REPLACE PROCEDURE FYI_CENTER AS sys_cur SYS_REFCURSOR; PROCEDURE emp_print(cur SYS_REFCURSOR) AS emp_rec employ... 2018-07-18, 2564🔥, 0💬

Define Anonymous Procedures with Variables in Oracle
How To Define an Anonymous Procedure with Variables in Oracle? Anonymous procedure is a procedure without any name. If you have some variables to declare, you can define an anonymous procedure by using the DECLARE keyword in SQL*Plus as shown in the following tutorial script: SQL&gt; set servero... 2018-01-27, 2562🔥, 0💬

Use NULL as Conditions in Oracle
How To Use NULL as Conditions in Oracle? If you want to compare values against NULL as conditions, you should use the "IS NULL" or "IS NOT NULL" operator. Do not use "=" or "&lt;&gt;" against NULL. The sample script below shows you some good examples: SELECT 'A' IS NULL FROM DUAL; -- Error: ... 2019-12-02, 2557🔥, 0💬

Define Default Values for Formal Parameters in Oracle
How To Define Default Values for Formal Parameters in Oracle? If you have an IN parameter, you can make it as an optional parameter for the calling statement by defining the formal parameter with the DEFAULT clause. This gives you the freedom of not providing the actual parameter when calling this p... 2018-10-19, 2556🔥, 0💬

Install Oracle SQL Developer in Oracle
How To Install Oracle SQL Developer in Oracle? Once you have sqldeveloper-v1.0.0.zip downloaded, extract the zip file into the root directory: \. When the extraction is done, the installation is completed. Your copy of Oracle SQL Developer is installed in directory: \sqldeveloper, and ready to run. ... 2019-02-05, 2555🔥, 0💬

Install Oracle SQL Developer in Oracle
How To Install Oracle SQL Developer in Oracle? Once you have sqldeveloper-v1.0.0.zip downloaded, extract the zip file into the root directory: \. When the extraction is done, the installation is completed. Your copy of Oracle SQL Developer is installed in directory: \sqldeveloper, and ready to run. ... 2019-02-05, 2555🔥, 0💬

Unlock the Sample User Account in Oracle
How To Unlock the Sample User Account in Oracle? Your 10g XE server comes with a sample database user account called HR. But this account is locked. You must unlock it before you can use it: Log into the server home page as SYSTEM. Click the Administration icon, and then click Database Users. Click ... 2020-09-30, 2553🔥, 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, 2551🔥, 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, 2548🔥, 0💬

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General MySQL Oracle SQL Server