General MySQL Oracle SQL Server

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Use Multiple Columns in GROUP BY in Oracle
Can Multiple Columns Be Used in GROUP BY in Oracle? You can use multiple columns in the GROUP BY clause as shown in the following example. It returns how many employees are having the same salary in each department: SQL&gt; SELECT department_id, salary, count(*) 2 FROM employees GROUP BY departm... 2019-10-27, 4061🔥, 0💬

How To Count Duplicated Values in a Column? in SQL Server
How To Count Duplicated Values in a Column in SQL Server? If you have a column with duplicated values, and you want to know what are those duplicated values are and how many duplicates are there for each of those values, you can use the "GROUP BY ... HAVING" clause as shown in the following example.... 2016-10-25, 4061🔥, 0💬

Import One Table back from a Dump File in Oracle
How To Import One Table Back from a Dump File in Oracle? If you only want to import one table back to the database, you can use a dump file that was created by full export, schema export or a table export. The following tutorial exercise shows you how to import the "fyi_links" table from a dump file... 2016-10-15, 4060🔥, 0💬

Get System Date and Time in SQL Server Transact-SQL
How to get system date and time in SQL Server Transact-SQL? I want a list of functions for getting current system date and time. Here is a comparison of all functions that you can use to get the current date and time from the data base server system: Function Return type Precision ------------------... 2017-02-25, 4058🔥, 0💬

Retrieve CREATE TABLE Statement with SQL Developer in Oracle
How To Get a CREATE Statement for an Existing Table in Oracle? You have an existing table and want to get a CREATE statement for that table, you can use the SQL tab in the object view. The following tutorial steps show you how to use SQL Developer to generate a CREATE statement on an existing table:... 2018-10-08, 4055🔥, 0💬

UPDATE with Subquery Returning No Rows in MySQL
What Happens If the UPDATE Subquery Returns No Rows in MySQL? If you use a subquery to assign new values in the SET clause in an UPDATE statement, and the subquery returns no rows for an outer row, MySQL will provide a NULL value to the SET clause. The tutorial exercise below shows you a good exampl... 2018-01-08, 4036🔥, 0💬

Understanding SQL Transaction Management in Oracle
Where to find answers to frequently asked questions on SQL Transaction Management in Oracle? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on SQL Transaction Management in Oracle. Clear answers are provided with tutorial exercises on starting and e... 2019-09-16, 4032🔥, 0💬

Change Transaction Isolation Level in MySQL
How To View and Change the Current Transaction Isolation Level in MySQL? If you want to view or change the current transaction isolation level, you can use the following commands: SELECT @@TX_ISOLATION FROM DUAL; -- Viewing the current transaction isolation level. SET TRANSACTION ISOLATION LEVEL lev... 2017-08-08, 4032🔥, 0💬

What Is SQL Language
What Is SQL Language? SQL, SEQUEL (Structured English Query Language), is a language for RDBMS (Relational Database Management Systems). During the 1970s, a group at IBM's San Jose research center developed a database system "System R" based upon Codd's model. Structured English Query Language ("SEQ... 2017-06-16, 4028🔥, 0💬

Query Multiple Tables Jointly in MySQL
How To Query Multiple Tables Jointly in MySQL? If you want to query information stored in multiple tables, you can use the SELECT statement with a WHERE condition to make an inner join. Assuming that you have 3 tables in a forum system: "users" for user profile, "forums" for forums information, and ... 2017-06-23, 4015🔥, 0💬

What Is a Database Table in Oracle
What Is a Database Table in Oracle? A database table is a basic unit of data logical storage in an Oracle database. Data is stored in rows and columns. You define a table with a table name, such as employees, and a set of columns. You give each column a column name, such as employee_id, last_name, a... 2020-11-22, 4012🔥, 0💬

What Is a Table Index in Oracle
What Is a Table 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 acce... 2020-11-22, 4010🔥, 0💬

SUM() - Total Value in Group
How to calculate the total value of a field expression in result set groups using the SUM() function? SUM(expr) is a MySQL built-in aggregate function that calculates the total value of a field expression in result set groups. For example: SELECT help_category_id, SUM(help_topic_id), COUNT(help_topi... 2023-12-01, 4002🔥, 0💬

Calculating the Difference between Two Time Values in MySQL
How To Calculate the Difference between Two Time Values in MySQL? If you have two time values, and you want to know the time difference between them, you can use the TIMEDIFF(time1, time2) function as shown below: SELECT TIMEDIFF(TIME('19:26:50'), TIME('09:26:50')) FROM DUAL; 10:00:00 SELECT TIMEDIF... 2017-12-26, 3992🔥, 0💬

Define External Table in a Text File in Oracle
How To Define an External Table in a Text File in Oracle? You can use the CREATE TABLE statement to create external tables. But you need to use ORGANIZATION EXTERNAL clause to specify the external file location and the data access driver. The tutorial exercise below shows you how to define an extern... 2016-10-19, 3987🔥, 1💬

💬 2016-10-19 Randy: Great example, Thanks!

Error: Single-Row Subquery Returns More Than One Row in Oracle
What Happens If the UPDATE Subquery Returns Multiple Rows in Oracle? If a subquery is used in a UPDATE statement, it must return exactly one row for each row in the update table that matches the WHERE clause. If it returns multiple rows, Oracle server will give you an error message. To test this out... 2020-01-21, 3972🔥, 0💬

Entering Date and Time Values in SQL Server
How To Enter Date and Time values in SQL Server Transact-SQL? Transact-SQL does not support date and time literals. If you want to enter date and time values, you have to use character string literals and rely implicit casting rules to convert them into date and time values. When casting character s... 2017-04-15, 3971🔥, 0💬

Overflow and Rounding on NUMERIC Values in SQL Server Transact-SQL
How Extra Digits Are Handled with NUMERIC Data Type Literals in SQL Server Transact-SQL? Exact numeric data types defined with NUMERIC(p,s) has two limits defined by two parameters: p (precision) and s (scale): Maximum number of digits of the integer part (digits before the decimal point) is defined... 2017-04-19, 3970🔥, 0💬

"CREATE PROCEDURE" - Creating Simple Stored Procedures in SQL Server
How To Create a Simple Stored Procedure in SQL Server Transact-SQL? If you want to create a simple stored procedure with no input and output parameters, you can use the "CREATE PROCEDURE" command with a statement batch in a simple format as shown in below: CREATE PROCEDURE procedure_name AS statemen... 2017-01-05, 3967🔥, 0💬

CREATE TABLE - Creating New Tables in SQL Server
How to create new tables with "CREATE TABLE" statements in SQL Server? If you want to create a new table, you can use the "CREATE TABLE" statement. The following tutorial script shows you how to create a table called "tip": CREATE TABLE tip (id INTEGER PRIMARY KEY, subject VARCHAR(80) NOT NULL, desc... 2016-11-17, 3965🔥, 0💬

Introduction to Oracle Database 10g Express Edition
Where to find answers to frequently asked questions on Oracle Database 10g Express Edition? I want to learn how to install Oracle database. Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Oracle Database 10g Express Edition with installation instr... 2020-05-15, 3948🔥, 0💬

Drop a Stored Function in Oracle
How To Drop a Stored Function in Oracle? If there is an existing stored function and you don't want it any more, you can remove it from the database by using the DROP FUNCTION statement as shown in the following script example: SQL&gt; CREATE OR REPLACE FUNCTION GET_SITE 2 RETURN VARCHAR2 AS 3 B... 2018-10-26, 3945🔥, 0💬

"sp_columns" - Getting a List of Columns in a View in SQL Server
How To Get a List of Columns in a View using the "sp_columns" Stored Procedure in SQL Server? If you have an existing table, but you don't remember what are the columns defined in the view, you can use the "sp_columns" stored procedure to get a list of all columns of the specified view. The followin... 2016-11-05, 3944🔥, 0💬

Export Data to a CSV File in Oracle
How To Export Data to a CSV File in Oracle? If you want to export data from a table to a file in CSV format, you can use the following steps: Right-click the table name, EMPLOYEES, in the object tree view. Select Export. Select CSV. The Export Data window shows up. Click Format tab. Select Format as... 2019-01-26, 3943🔥, 0💬

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General MySQL Oracle SQL Server