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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, 650👍, 0💬

Adding a New Index to a Large Table in SQL Server
What Happens If You Add a New Index to Large Table in SQL Server? An index can be added when you create a new table. New rows will be indexed as they are inserted into the table. But you can also add a new index to an existing table with the same CREATE INDEX statement. The existing rows will be ind...
2016-11-13, 650👍, 0💬

Shutdown MySQL Server Properly in MySQL
How To Properly Shutdown MySQL Server Daemon mysqld in MySQL? The proper way to shutdown your MySQL server is to the use "mysqladmin shutdown" command. Other ways to shutdown your server include: Enter "mysqladmin -u root -ppassowrd shutdown" command with options in a command window. Use Windows Tas...
2017-12-04, 649👍, 0💬

Restore Tables by Copying MyISAM Files in MySQL
How To Restore Tables by Copying MyISAM Table Files in MySQL? If you have old copies of MyISAM table files, you can restore them easily by copying them back to the data directory to replace the current table files. However you may need to shut down MySQL server to do this, because the current table ...
2017-09-01, 649👍, 0💬

Creating Local Temporary Stored Procedures in SQL Server
How To Create a Local Temporary Stored Procedure in SQL Server Transact-SQL? A local temporary stored procedure is a special stored procedure that: Is created like a normal (permanent) stored procedure with the name prefixed with a number sign (#). Are only valid in the same client session where it ...
2016-12-28, 649👍, 0💬

Turn on Query Logs in MySQL
How To Turn on Query Logs in MySQL? If you want MySQL to write query logs to a file, you can use the "--log=fileName" option at the "mysqld" command line. The tutorial exercise below shows you a good example on how to use this option and view the query log file: &gt;cd \mysql\bin &gt;mkdir \...
2017-12-04, 647👍, 0💬

Measuring Performance of INSERT Statements in SQL Server
How To Measure Performance of INSERT Statements in SQL Server? When indexes are defined for a table, each time a new row is inserted to the table, all the indexes must be updated. This extra update work could slow down the insert statement. To find out how much slower the INSERT statements will be o...
2016-11-13, 647👍, 0💬

Testing Table for SELECT Statements in SQL Server
How To Create a Testing Table with Test Data to try with SELECT statements in SQL Server? If you want to follow the tutorial exercises presented in this collection, you need to create a testing table and insert some test data, as shown in the following sample script: CREATE TABLE fyi_links (id INTEG...
2016-10-26, 647👍, 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, 646👍, 0💬

Defragmenting Table Indexes in SQL Server
How To Defragment Table Indexes in SQL Server? When a table index is fragmented to a certain percentage, you need to defragment the index to maintain its performance level. There are 3 ways to defragment: 1. "ALTER INDEX index_name ON table_name REORGANIZE" - Defragmenting the specified index perfor...
2016-11-08, 646👍, 0💬

Creating a Logon Trigger in Express Edition in SQL Server
Can You Create a Logon Trigger in SQL Server 2005 Express Edition in SQL Server? Can you create a logon trigger in SQL Server 2005 Express Edition? The answer is no. LOGON is not a supported event type in Express Edition. The script below shows you the error message when you try to create a logon tr...
2016-10-22, 646👍, 0💬

LIKE - Matching a Pattern in a Character String in SQL Server
What To Perform Pattern Match with the LIKE Operator in SQL Server Transact-SQL? Pattern match is a very important operation for search records base on character string columns. SQL Server 2005 offers the LIKE operator to perform pattern match operations in two formats: target_string LIKE pattern --...
2017-01-21, 645👍, 0💬

Defining and Using Table Alias Names in SQL Server
How To Define and Use Table Alias Names in SQL Server? When column names need to be prefixed with table names, you can define table alias name and use them to prefix column names. To define an alias for a table name, just enter the alias name right after the original table name in the FROM clause as...
2016-10-30, 645👍, 0💬

"CREATE LOGIN" - Creating a New Login Name in SQL Server
How To Create a New Login Name in SQL Server in SQL Server? In previous tutorials, it is assumed that you use the "sa" (System Administrator) login name to connect to your SQL Server. But that is not what a normal developer uses to connect to the server, since "sa" has the ALL permissions granted. Y...
2016-10-20, 645👍, 0💬

Read Consistency in Oracle in Oracle
How Does Oracle Handle Read Consistency in Oracle? Oracle supports two options for you on how to maintain read consistency: READ WRITE (the default option), also called statement-level read consistency. READ ONLY, also called transaction-level read consistency.   ⇒Understanding SQL Transaction Manag...
2019-08-23, 643👍, 0💬

Retrieve Field Values from RECORD Variables in Oracle
How To Retrieve Values from Data Fields in RECORD Variables in Oracle? If a variable is a RECORD variable with data fields assigned values, you can retrieve those values out of its data fields by using fields names prefixed with variable name as "variable.field_name". Here is a sample script showing...
2018-09-01, 643👍, 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, 643👍, 0💬

Update Values in a Table in Oracle
How To Update Values in a Table in Oracle? If you want to update some values in one row or multiple rows in a table, you can use the UPDATE statement. The script below shows a good example: UPDATE fyi_links SET counts = 999, notes = 'Good site.' WHERE id = 101; 1 row updated. SELECT * FROM fyi_links...
2020-01-21, 642👍, 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, 642👍, 0💬

Differences between Functions and Stored Procedures in SQL Server
What Are the Differences between User Defined Functions and Stored Procedures in SQL Server Transact-SQL? Differences between user defined functions and stored procedures are: Stored procedures does not return any data and they can not be used in expressions. User defined functions does return data ...
2016-12-24, 642👍, 0💬

Creating an Index for Multiple Columns in SQL Server
How To Create an Index for Multiple Columns in SQL Server? An index for multiple columns works similarly to a sorting process on multiple columns. If an index is defined for two columns, the index key is composed by values from those two columns. A multi-column index will be used to speed up the sea...
2016-11-13, 642👍, 0💬

Sorting Query Output by Multiple Columns in SQL Server
Can the Query Output Be Sorted by Multiple Columns in SQL Server? You can specifying multiple columns in the ORDER BY clause as shown in the following example statement, which returns rows sorted by "tag" and "counts" values: SELECT tag, counts, url, created FROM fyi_links ORDER BY tag, counts GO ta...
2016-10-26, 642👍, 0💬

Create a New View in MySQL
How To Create a New View in MySQL? You can create a new view based on one or more existing tables by using the "CREATE VIEW viewName AS selectStatement" statement as shown in the following script: mysql&gt; CREATE TABLE comment (faqID INTEGER, message VARCHAR(256)); Query OK, 0 rows affected (0....
2018-01-24, 641👍, 0💬

Listing All User Accounts in MySQL
How To List All Existing User Accounts in MySQL? MySQL stores all existing user accounts in a table called "mysql.user". If you want see all user accounts, you can use the "SELECT" command as shown in the tutorial exercise below: &gt;cd \mysql\bin &gt;mysql -u root -pretneciyf mysql mysql&am...
2017-12-13, 641👍, 0💬

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