General MySQL Oracle SQL Server

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Inner Join with the WHERE Clause in Oracle
How To Write an Inner Join with the WHERE Clause in Oracle? If you don't want to use the INNER JOIN ... ON clause to write an inner join, you can put the join condition in the WHERE clause as shown in the following query example: SQL&gt; SELECT d.department_name, e.first_name, e.last_name 2 FROM... 2019-10-18, 2768🔥, 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, 2767🔥, 0💬

Data File for InnoDB Storage Engine in MySQL
Where Table Data Is Stored by the InnoDB Storage Engine in MySQL? By default, MySQL provides \mysql\data directory for all storage engines to store table data. Under \mysql\data directory, InnoDB storage engine will create 3 files to store and manage all tables that use the InnoDB storage engine: ib... 2017-08-13, 2765🔥, 0💬

SP_HELP - Viewing Existing Indexes on an Given Table in SQL Server
How To View Existing Indexes on an Given Table using SP_HELP in SQL Server? If you want to know how many indexes have been defined for a given table, you can use the SP_HELP built-in stored procedure in the following syntax: EXEC SP_HELP table_name -- Returns all database objects related the given t... 2016-11-15, 2765🔥, 0💬

Privilege Needed to Connect to Oracle Server in Oracle
What Privilege Is Needed for a User to Connect to Oracle Server in Oracle? Oracle deny connection to users who has no CREATE SESSION privilege. Try the following tutorial exercise, you will find out how Oracle denies connection: &gt;.\bin\sqlplus /nolog SQL&gt; connect SYSTEM/fyicenter SQL&a... 2019-07-09, 2764🔥, 0💬

Use Existing Column Values in the SET Clause in MySQL
How To Use Existing Column Values in the SET Clause in MySQL? If a row matches the WHERE clause in a UPDATE statement, existing values in this row can be used in expressions to provide new values in the SET clause. Existing values are represented by column names in the expressions. The tutorial exer... 2018-01-13, 2764🔥, 0💬

List Table Names with "mysqlshow" Command in MySQL
How To Show Table Names with "mysqlshow" in MySQL? If you want to show table names with "mysqlshow", you need to specify a database name. The followings tutorial exercise shows you how to get all table names that match a pattern: If you want analyze tables with "mysqlcheck", you need to use the "--a... 2018-05-19, 2761🔥, 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, 2760🔥, 0💬

BETWEEN - Testing Value in a Range in SQL Server
What To Test Value Ranges with the BETWEEN Operator in SQL Server Transact-SQL? Sometimes you want to compare a value against a value range. You can do this with two regular comparison operations. But you can also use the special comparison operator BETWEEN to get it done with the following syntaxes... 2017-01-21, 2760🔥, 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, 2759🔥, 0💬

What are Date and Time Data Types in MySQL
What Are Date and Time Data Types in MySQL? MySQL supports the following date and time data types: DATE - A date in the range of '1000-01-01' and '9999-12-31'. Default DATE format is "YYYY-MM-DD". DATETIME - A date with the time of day in the range of '1000-01-01 00:00:00' and '9999-12-31 23:59:59'.... 2018-03-24, 2759🔥, 0💬

CREATE INDEX - Impact on Other User Sessions in SQL Server
What Is the Impact on Other User Sessions When Creating Indexes in SQL Server? If you are creating a new index on a table with existing data, all existing rows will be indexed as part of the CREATE INDEX statement. If the table is large, the indexing process could take some time. The impact of this ... 2016-11-08, 2757🔥, 0💬

Differences of CHAR and VARCHAR in SQL Server Transact-SQL
What Are the Differences between CHAR and VARCHAR in SQL Server Transact-SQL? CHAR and VARCHAR are both used to store code page based 1-byte character strings in Transact-SQL. But they have the following main differences: CHAR(n) stores character strings with a fixed length, n bytes, storage format.... 2017-04-04, 2755🔥, 0💬

odbc_exec() - Executing SQL Statements
How To Execute a SQL Statement using odbc_exec()? Once you have created an ODBC connection object, you can use the odbc_exec() function to send a SQL statement to the SQL Server linked to the connection object for execution. Here is a simple PHP script that creates a new schema and a new table: &... 2024-06-30, 2754🔥, 0💬

Deleting an Existing Database in MySQL
How To Drop an Existing Database in MySQL? If want to drop an existing database from the MySQL server, you can use the DROP DATABASE statement. Here is a good example of dropping an existing database: $con = mysql_connect('localhost:8888' ,'dev', 'iyf'); $sql = 'DROP DATABASE fyi'; if (mysql_query($... 2017-10-23, 2754🔥, 0💬

What Is a Dead Lock in MySQL
What Is a Dead Lock in MySQL? A dead lock is phenomenon happens between two transactions with each of them holding a lock that blocks the other transaction as shown in the following diagram: (transaction 1) (transaction 2) update row X to create lock 1 update row Y to create lock 2 update row X (blo... 2017-04-28, 2753🔥, 0💬

Importance of Column Order in the SET Clause in Update Statements in SQL Server
Is the Order of Columns in the SET Clause Important in SQL Server? The answer is NO. The order of columns in the SET clause of the UPDATE statement is NOT important. You probably already noticed from the previous tutorial. There is a BIG DIFFERENCE among SQL Server, MySQL and Oracle on update multip... 2016-11-02, 2753🔥, 0💬

What Are NULL Values in SQL Server
What Are NULL Values in SQL Server Transact-SQL? A NULL value is a special value that represents an unknown value. SQL Server supports NULL values with the following features: All data types used for table columns support NULL values. In another word, NULL values can be stored in database tables. In... 2017-02-05, 2752🔥, 0💬

Relation between Database and Tablespaces in Oracle
How a Database Is Related to Tablespaces in Oracle? A database's data is collectively stored in the datafiles that constitute each tablespace of the database. For example, the simplest Oracle database would have one tablespace and one datafile. Another database can have three tablespaces, each consi... 2019-01-20, 2751🔥, 0💬

Logical Operations in PL/SQL in Oracle
What Are the Logical Operations in Oracle? PL/SQL supports 3 logical operations as shown in the following sample script: PROCEDURE proc_comparison AS x BOOLEAN := TRUE; y BOOLEAN := FALSE; res BOOLEAN; BEGIN res = x AND y; res = x OR y; res = NOT x; -- more statements END;   ⇒ Categories of Data Typ... 2018-08-06, 2751🔥, 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, 2749🔥, 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, 2749🔥, 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, 2749🔥, 0💬

Quoting Text Values in MySQL
How To Quote Text Values in SQL Statements in MySQL? Text values in SQL statements should be quoted with single quotes ('). If the text value contains a single quote ('), it should be protected by replacing it with two single quotes (''). In SQL language syntax, two single quotes represents one sing... 2017-06-28, 2749🔥, 0💬

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General MySQL Oracle SQL Server