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MySQL Articles
Page 75 of 355
In MySQL, how it can be possible to specify a sort order using a column that is not retrieved by the query?
Actually, as we know that we can specify a sort order with the help of the ORDER BY clause. We need to write the ORDER BY keyword followed by the name of the column on which we want to sort the table. It is not necessary that we have to use that column name after the SELECT keyword in the query.Examplemysql> Select Sr, Item from ratelist ORDER BY Price; +----+------+ | Sr | Item | +----+------+ | 5 | T | | 1 | A | | 2 | B | | 4 | h | ...
Read MoreHow the MySQL command that you are in the process of entering can be canceled?
Suppose if we do not want to execute a command that we are entering, then we can use a clear \c option which clears the current input. For example, the use of \c option can be done as follows −mysql> Select * -> from\cIn the example above, when we use \c in a statement, MySQL clears the current input and returns back to the MySQL prompt for accepting other statements.
Read MoreHow can we convert subqueries to INNER JOIN?
To make it understand we are using the data from the following tables −mysql> Select * from customers; +-------------+----------+ | Customer_Id | Name | +-------------+----------+ | 1 | Rahul | | 2 | Yashpal | | 3 | Gaurav | | 4 | Virender | +-------------+----------+ 4 rows in set (0.00 sec) mysql> Select * from reserve; +------+------------+ | ID | Day | +------+------------+ | 1 | 2017-12-30 | | ...
Read MoreWhat are the different MySQL prompts we have on the command line?
As we know that after writing the first line of multiple-line queries, MySQL changes the prompt. The following table shows different MySQL prompts and it's meaning −PromptMeaning mysql>It means MySQL is ready for a new command. →It means that MySQL is waiting for the next line of multiple-line command. ‘>It means that MySQL is waiting for the next line, waiting for the completion of a string that began with a single quote. “>It means that MySQL is waiting for the next line, waiting for the completion of a string that began with a double quote. `>It means that MySQL is waiting ...
Read MoreHow can we use two columns with MySQL WHERE clause?
It is very rarely used to use two columns of the same table in WHERE clause but still we can perform a query with two columns of the same table. Consider the below example −mysql> Select F_name, L_name -> From Customer -> where F_name = L_name; Empty set (0.00 sec)Here we are using both the columns(F_Name and L_Name) from the same table(Customer) hence the result is an Empty set.
Read MoreHow can we convert subqueries to LEFT JOIN?
To make it understand we are using the data from the following tables −mysql> Select * from customers; +-------------+----------+ | Customer_Id | Name | +-------------+----------+ | 1 | Rahul | | 2 | Yashpal | | 3 | Gaurav | | 4 | Virender | +-------------+----------+ 4 rows in set (0.00 sec) mysql> Select * from reserve; +------+------------+ | ID | Day | +------+------------+ | 1 | 2017-12-30 | | ...
Read MoreHow can we run a MySQL statement without termination semicolon?
With the help of \G or \g option just at the end of the MySQL statement, we can run it without the semicolon. Consider the example below −mysql> Select * from Stock_item\G *************************** 1. row *************************** item_name: Calculator Value: 15 Quantity: 89 *************************** 2. row *************************** item_name: Notebooks Value: 63 Quantity: 40 *************************** 3. row *************************** item_name: Pencil Value: 15 Quantity: 40 *************************** 4. row *************************** item_name: Pens Value : 65 Quantity: 32 *************************** 5. row *************************** item_name: Shirts Value: 13 Quantity: 29 *************************** 6. row *************************** item_name: Shoes ...
Read MoreHow can we convert subqueries to RIGHT JOIN?
To make it understand we are using the data from the following tables −mysql> Select * from Customers; +-------------+----------+ | Customer_Id | Name | +-------------+----------+ | 1 | Rahul | | 2 | Yashpal | | 3 | Gaurav | | 4 | Virender | +-------------+----------+ 4 rows in set (0.00 sec) mysql> Select * from Reserve; +------+------------+ | ID | Day | +------+------------+ | 1 | 2017-12-30 | | ...
Read MoreWhat are the restrictions, in terms of a number of rows and columns, with MySQL query having no table list?
The restriction on MySQL query having a notable list is that it can return, as a result, exactly one row but that result can contain multiple columns.Examplemysql> Select 65/NULL,65+NULL,65*NULL,65-NULL,65%NULL; +------------+--------------+-------------+-------------+---------+ | 65/NULL | 65+NULL | 65*NULL | 65-NULL | 65%NULL | +------------+--------------+-------------+-------------+---------+ | NULL | NULL | NULL | NULL | NULL | +------------+--------------+-------------+-------------+---------+ 1 row in set (0.00 sec)In the above example, we can see that MySQL returns only one row with five columns, having the result of five expressions, as a result when we do not have any table list in the statement.
Read MoreIn a Multiple-line query, what is the significance of the change of MySQL prompt after the first line?
After writing the first line of multiple-line queries, MySQL changes promptly from ‘mysql>’ to ‘→’. It is significant because with the help of it we got an indication that MySQL has not seen a complete statement yet and is waiting for the rest. Consider the example below,mysql> Select * -> from -> stock_item;We know that after writing the first line i.e. ‘Select *’ Mysql changes its prompts which means that yet the state has not been completed. After the semicolon, MySQL considers the statement completed and throws the output.
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