General MySQL Oracle SQL Server

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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, 3273🔥, 0💬

Test NULL Values in Oracle
How To Test NULL Values in Oracle? There ate two special comparison operators you can use on NULL values: "variable IS NULL" - Returns TRUE if the variable value is NULL. "variable IS NOT NULL" - Return TRUE if the variable value is not NULL. The following sample script shows you examples of compari... 2018-07-13, 3272🔥, 0💬

Run-Away Recursive Calls in Oracle
What Happens If Recursive Calls Get Out of Control in Oracle? What happens if your code has bug on recursive procedure calls, which causes an infinite number nested procedure calls? The answer is not so good. Oracle server seems to offer no protection calling stack limit. The script below shows you ... 2018-03-18, 3272🔥, 0💬

What Is the Implicit Cursor in Oracle
What Is the Implicit Cursor in Oracle? There is only one implicitly cursor in a session. The implicit cursor is the cursor automatically defined by PL/SQL for you. Whenever a SQL statement is executed, this cursor will be assigned to represent the execution of this statement. This implicit cursor is... 2018-02-01, 3270🔥, 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, 3267🔥, 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, 3265🔥, 0💬

Install Oracle ODBC Drivers in Oracle
How To Install Oracle ODBC Drivers in Oracle? Oracle offers different ODBC drivers for different versions of Oracle servers. When you install an Oracle server or a client tools on your Windows system, the appropriate ODBC driver will be installed for you automatically. If you want to install a speci... 2016-10-15, 3255🔥, 0💬

Clean Up When CREATE DATABASE Failed in Oracle
How To Do Clean Up If CREATE DATABASE Failed in Oracle? To better organize data files, you should create a dedicated directory for each Oracle database. This can be done by using Windows file explorer to create the \oraclexe\oradata\fyi\ directory. Try the CREATE DATABASE statement again, when you h... 2019-03-27, 3250🔥, 0💬

Cannot Use DDL Statements in PL/SQL in Oracle
Can DDL Statements Be Used in PL/SQL in Oracle? No, you can not run any DDL statements is PL/SQL directly. If you try to use the DROP TABLE statement inside PL/SQL, you will get a compilation error as shown below: (Connect to XE with SQL*Plus) BEGIN DROP TABLE student; -- compilation error END; /   ... 2018-10-13, 3247🔥, 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, 3240🔥, 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, 3238🔥, 0💬

Relations between a Tablespace and Data Files in Oracle
How a Tablespace Is Related to Data Files in Oracle? Each tablespace in an Oracle database consists of one or more files called datafiles, which are physical structures that conform to the operating system in which Oracle is running.   ⇒ Relation between Database and Tablespaces in Oracle ⇐ Oracle ... 2019-01-20, 3234🔥, 0💬

What Is a Cursor Variable in Oracle
What Is a Cursor Variable in Oracle? A cursor variable is a variable of a specific REF CURSOR data type, which is a pointer to a data structure resource connects to query statement result, similar to the CURSOR data type.. The advantage of using cursor variables is that cursor variables can be used ... 2018-04-07, 3234🔥, 0💬

Call a Stored Function in Oracle
How To Call a Stored Function in Oracle? A stored function can be called as part of expression in any PL/SQL statement. One simplest way to call a stored function is to a dummy SELECT statement as shown in the following tutorial script using SQL*Plus: SQL&gt; CREATE OR REPLACE FUNCTION GET_SITE ... 2018-10-26, 3230🔥, 0💬

Use FETCH Statement in a Loop in Oracle
How To Use FETCH Statement in a Loop in Oracle? If you have a cursor opened ready to use, you can also use the FETCH statement in a loop to retrieve data from the cursor more efficiently. But you need to remember to use an EXIT statement break the loop when the cursor pointer reaches the end. The sc... 2018-04-07, 3230🔥, 0💬

Systems Supported by 10g XE Server in Oracle
What Operating Systems Are Supported by Oracle Database 10g XE in Oracle? Oracle Database 10g Express Edition is available for two types of operating Systems: Linux x86 - Debian, Mandriva, Novell, Red Hat and Ubuntu Microsoft Windows   ⇒ Download Oracle Database 10g XE in Oracle ⇐ Limitations of Or... 2020-05-05, 3229🔥, 0💬

What Is a RECORD in PL/SQL in Oracle
What Is a RECORD in PL/SQL in Oracle? RECORD is a composite data type in PL/SQL. It can have many fields representing data elements with different data types. Variables of RECORD type can be designed to hold data from database table rows. To use RECORD data type, you need to define a specific RECORD... 2018-09-13, 3228🔥, 0💬

Run CREATE DATABASE Statement in Oracle
How To Run CREATE DATABASE Statement in Oracle? This is Step 7. Oracle Administrator Guide provided a sample CREATE DATABASE statement. But it is a long statement. You can modify and same it in a file, $ORACLE_HOME/configscripts/cre ate_database_fyi.sql,and run the file within SQL*Plus. Here is a co... 2018-05-08, 3228🔥, 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, 3226🔥, 0💬

Use "IF" Statements with Multiple Conditions in Oracle
How To Use "IF" Statements on Multiple Conditions in Oracle? If you have multiple blocks of codes to be executed based on different conditions, you can use the "IF ... ELSIF" statement. Here is a sample script on IF statements: DECLARE day VARCHAR2; BEGIN day := 'SUNDAY'; IF day = 'THURSDAY' THEN DB... 2018-07-13, 3226🔥, 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, 3225🔥, 0💬

Lock and Unlock a User Account in Oracle
How To Lock and Unlock a User Account in Oracle? If you want to lock a user account for a short period of time, and unlock it later, you can use the ALTER USER ... ACCOUNT command. The following sample script shows how to use this command: &gt;.\bin\sqlplus /nolog SQL&gt; connect SYSTEM/fyic... 2019-06-29, 3224🔥, 0💬

Convert Character Strings to Dates in Oracle
How To Convert Character Strings to Dates in Oracle? You can convert dates to characters using the TO_DATE() function as shown in the following examples: SELECT TO_DATE('07-MAY-2006', 'DD-MON-YYYY') FROM DUAL; 07-MAY-06 SELECT TO_DATE('2006/05/07 ', 'YYYY/MM/DD') FROM DUAL; 07-MAY-06 SELECT TO_DATE(... 2020-03-25, 3223🔥, 0💬

Bring a Tablespace Online in Oracle
How To Bring a Tablespace Online in Oracle? If you have brought a tablespace offline, now you want to make it available to users again, you can use the ALTER TABLESPACE ... ONLINE statement as shown in the following script: SQL&gt; connect HR/fyicenter SQL&gt; CREATE TABLESPACE my_space 2 DA... 2019-01-01, 3221🔥, 0💬

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General MySQL Oracle SQL Server