General MySQL Oracle SQL Server

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IN - Testing Values Returned by a Subquery in SQL Server
How To Test Values Returned by a Subquery with the IN Operator in SQL Server Transact-SQL? Normally, the comparison operator IN is used against a list of specified values as in the format of: "test_value IN (value_1, value_2, ..., value_n)". But you can also replace the list of values by a subquery ... 2017-01-21, 1329🔥, 0💬

SINGLE_USER/MULTI_USER - Database User Access Options in SQL Server
How to set database to be SINGLE_USER in SQL Server? Databases in SQL Server have three user access options: MULTI_USER - All users that have the appropriate permissions to connect to the database are allowed. This is the default. SINGLE_USER - One user at a time is allowed to connect to the databas... 2016-11-20, 1329🔥, 0💬

Creating and Managing Schemas in SQL Server
Where to find answers to frequently asked questions on Creating and Managing Schemas in SQL Server? Here is a list of frequently asked questions and their answers compiled by FYIcenter.com DBA team on Creating and Managing Schemas in SQL Server. Clear answers are provided with tutorial exercises on ... 2016-10-22, 1329🔥, 0💬

Selecting Other User's Database in MySQL
Can You Select Someone Else Database in MySQL? If your MySQL server is provided by an Internet service company, they will provide you one database for your use only. There are many other databases on the server for other users. But your user account will have no privilege to select other databases. ... 2017-10-23, 1328🔥, 0💬

Types of Table Joins in MySQL
How To Join Two Tables in a Single Query in MySQL? Two tables can be joined together in a query in 4 ways: Inner Join: Returns only rows from both tables that satisfy the join condition. Left Outer Join: Returns rows from both tables that satisfy the join condition, and the rest of rows from the fir... 2017-12-31, 1326🔥, 0💬

Expressions with NULL Values in MySQL
What Happens If NULL Values Are Involved in Expressions in MySQL? If NULL values are used in expressions, the resulting values will be NULL values. In other words: Arithmetic expressions with NULL values result NULL values. Comparison expressions with NULL values result NULL values. Logical expressi... 2018-03-28, 1325🔥, 0💬

Entering Numeric Values as HEX Numbers in MySQL
How To Enter Numeric Values as HEX Numbers in MySQL? If you want to enter numeric values as HEX numbers, you can quote HEX numbers with single quotes and a prefix of (X), or just prefix HEX numbers with (0x). A HEX number string will be automatically converted into a numeric value, if the expression... 2018-03-31, 1323🔥, 0💬

Sort by Multiple Columns in MySQL
Can the Query Output Be Sorted by Multiple Columns in MySQL? You can specifying multiple columns in the ORDER BY clause as shown in the following example statement, which returns employees' salaries sorted by department and salary value: mysql&gt; SELECT tag, counts, url, DATE(created) FROM fyi_... 2017-11-02, 1322🔥, 0💬

Close MySQL Connection Objects in MySQL
How To Close MySQL Connection Objects in MySQL? MySQL connection objects created with mysql_connect() calls should be closed as soon as you have finished all of your database access needs by calling mysql_close($con) function. This will reduce the consumption of connection resources on your MySQL se... 2017-11-11, 1320🔥, 0💬

Adding More Data to the Test Table in MySQL
How To Add More Data to the Testing Table in MySQL? If you want to continue with other tutorial exercises in this FAQ collection, you need to add more data to the testing table. Follow the script below to add a new column and: mysql&gt; ALTER TABLE fyi_links ADD COLUMN tag VARCHAR(8); mysql&... 2017-11-02, 1320🔥, 0💬

Using Values from Other Tables in UPDATE Statements in SQL Server
How To Use Values from Other Tables in UPDATE Statements in SQL Server? If you want to update values in one table with values from another table, you can use a subquery as an expression in the SET clause. The subquery should return only one row for each row in the update table that matches the WHERE... 2016-11-02, 1319🔥, 0💬

Selecting All Columns of All Rows in MySQL
How To Select All Columns of All Rows from a Table in MySQL? The simplest query statement is the one that selects all columns of all rows from a single table: "SELECT * FROM tableName;". The (*) in the SELECT clause tells the query to return all columns. The missing WHERE clause tells the query to r... 2017-11-05, 1317🔥, 0💬

Rename an Existing Table in MySQL
How To Rename an Existing Table in MySQL? If you want to rename an existing table, you can use the "ALTER TABLE ... RENAME TO" statement. The tutorial script below shows you a good example: mysql&gt; ALTER TABLE tip RENAME TO faq; Query OK, 0 rows affected (0.01 sec) mysql&gt; SELECT * FROM ... 2018-02-14, 1316🔥, 0💬

Creating a Simple Table to Test Triggers in SQL Server
How To Create a Simple Table to Test Triggers in SQL Server? If you want to follow other tutorial examples included in this collection, you need to run this SQL script to create a simple table called fyi_users: USE FyiCenterData; GO DROP TABLE fyi_users; GO CREATE TABLE fyi_users ( id INTEGER IDENTI... 2016-10-25, 1315🔥, 0💬

Rename an Existing User Account in MySQL
How To Rename an Existing User Account Name in MySQL? If you want to change the name of an existing user account, you can use the "RENAME USER oldName TO newName" command. The tutorial exercise below shows you how to do this: &gt;cd \mysql\bin &gt;mysql -u root -pretneciyf mysql mysql&gt... 2017-12-13, 1314🔥, 0💬

Rebuilding All Indexes on One Table in SQL Server
How To Rebuild All Indexes on a Single Table in SQL Server? If you have several indexes on a single table and want to rebuild all of them, you may use the "ALTER INDEX ALL ON table_name REBUILD" statement as shown in the tutorial exercise below: USE FyiCenterData; GO UPDATE fyi_links_indexed SET url... 2016-11-08, 1313🔥, 0💬

Filtering Out Duplications in the Returning Rows in SQL Server
How To Filter Out Duplications in the Returning Rows in SQL Server? If there are duplications in the returning rows, and you want to remove the duplications, you can use the keyword DISTINCT in the SELECT clause. The DISTINCT applies to the combination of all data fields specified in the SELECT clau... 2016-10-26, 1313🔥, 0💬

Group Functions in Query Statements in SQL Server
What Are Group Functions in Query Statements in SQL Server? Group functions are functions applied to a group of rows. Examples of group functions are: COUNT(*) - Returns the number of rows in the group. MIN(exp) - Returns the minimum value of the expression evaluated on each row of the group. MAX(ex... 2016-10-25, 1311🔥, 0💬

NULL Values Involved in String Operations in SQL Server
What Happens If NULL Values Are Involved in String Operations in SQL Server Transact-SQL? If NULL values are involved in string operations, the result will be string NULL values. The following tutorial script shows you some good examples: SELECT 'FyiCenter'+NULL; GO ---------- NULL SELECT LEN(NULL);... 2017-02-05, 1310🔥, 0💬

Assign Field Values into RECORD Variables in Oracle
How To Assign Values to Data Fields in RECORD Variables in Oracle? If a variable is a RECORD variable, you can assign values to its data fields by using fields names prefixed with variable name as "variable.field_name". Here is a sample script assigning values to data fields of RECORD variables: CRE... 2018-09-01, 1309🔥, 0💬

List All Tables with "mysql" Command in MySQL
How To Show All Tables with "mysql" in MySQL? If you want to see all the tables in a database, you run the non-SQL command "SHOW TABLES" at the "mysql" prompt. See the following tutorial exercise for example: &gt;cd \mysql\bin &gt;mysql -u root test Welcome to the MySQL monitor. Commands end... 2018-02-28, 1305🔥, 0💬

Deleting an Existing Row with DELETE Statements in SQL Server
How To Delete an Existing Row with DELETE Statements in SQL Server? If you want to delete an existing row from a table, you can use the DELETE statement with a WHERE clause to identify that row. Here is good sample of DELETE statements: -- insert a row for this test INSERT INTO fyi_links (url, id) V... 2016-10-30, 1303🔥, 0💬

What Are Triggers in SQL Server
What Are Triggers in SQL Server? A trigger is a special kind of stored procedure that automatically executes when an event occurs in the database server. A trigger is really an event handler. SQL Server allows users to create triggers (event handlers) for 3 types of events: DML Event - Occurs when a... 2016-10-25, 1303🔥, 0💬

Entering Microseconds in SQL Statements in MySQL
How To Enter Microseconds in SQL Statements in MySQL? If you want to enter microseconds in a SQL statements, you can enter them right after the time string as a 6-digit number delimited with '.'. '0' will be padded to right if not enough digits. Here are some good examples: SELECT TIME('1997/01/31 0... 2017-12-26, 1302🔥, 0💬

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General MySQL Oracle SQL Server