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Articles on Trending Technologies
Technical articles with clear explanations and examples
How can we test for the existence of any record in MySQL subquery?
We can use MySQL EXIST operator to test for the existence of a record in the subquery. In other words, we can say that EXIST operator checks if a subquery returns any rows. The syntax of using EXIST operator with MySQL subquery is as follows −SyntaxWHERE EXISTS (Subquery)The above EXIST (subquery) expression returns TRUE if the subquery returns at least one row, otherwise it returns false.ExampleTo make it understand we are using the data from the following tables −mysql> Select * from Customers; +-------------+----------+ | Customer_Id | Name | +-------------+----------+ | 1 | ...
Read MoreHow MySQL evaluates if we use EXISTS operator with the subquery that returns NULL?
If a subquery, used with EXIST operator, returns NULL, the expression EXIST NULL returns TRUE and MySQL returns the result based on an outer query. It can be understood with the help of simple example using the following data from table ‘Customers’ −mysql> Select * from Customers; +-------------+----------+ | Customer_Id | Name | +-------------+----------+ | 1 | Rahul | | 2 | Yashpal | | 3 ...
Read MoreHow can we nest a subquery within another subquery?
If a subquery is nested inside another subquery then it is called a nested subquery. To make it understand we are creating the nested subquery from the following tables data −mysql> Select * from Cars; +------+--------------+---------+ | ID | Name | Price | +------+--------------+---------+ | 1 | Nexa | 750000 | | 2 | Maruti Swift | 450000 | | 3 | BMW ...
Read MoreWhat are single row and multiple row subqueries?
Single Row Sub QueryA single-row subquery is used when the outer query's results are based on a single, unknown value. Although this query type is formally called "single-row, " the name implies that the query returns multiple columns-but only one row of results. However, a single-row subquery can return only one row of results consisting of only one column to the outer query.In the below SELECT query, inner MySQL returns only one row i.e. the minimum salary for the company. It, in turn, uses this value to compare the salary of all the employees and displays only those, whose salary ...
Read MoreFinding a database view in SAP HANA database
This is created under the Current schema in your SQL editor. You can check schema name at the top −In the above snapshot, you can see the current schema name where the view is created. You need to find this schema under the Catalog folder in HANA Studio.
Read MoreExample of creating a database view in SAP HANA
Let us see the below table ARTICLE_LOOKUP, we will create a database view with first 4 columns and will hide Family_NAME and FAMILY_CODE.SQL statement- To create a view on the above table, write down the below SQL statementcreate view view_Articlelookup as select ARTICLE_ID,ARTICLE_LABEL,CATEGORY,SALE_PRICE from "AA_HANA11"."ARTICLE_LOOKUP";This will create a database view in the mentioned schema and you can check it in Views folder (schema name here-AA_HANA11). You can see a view with the name- view_Articlelookup and only 4 data columns are there.
Read MoreWhat are the synonym statements of MySQL DESCRIBE?
Followings are the synonyms statements of MySQL DESCRIBE i.e. the statements with the help of which we can get the same kind of information/structure of the table as we get from DESCRIBE −EXPLAIN StatementEXPLAIN is the synonym of the DESCRIBE statement. Its syntax is also similar to the DESCRIBE statement. Consider the following example −mysql> Explain Employee; +-------+-------------+------+-----+---------+------------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+------------------+ | ID | int(11) | NO | PRI | NULL | auto_increment | | ...
Read MoreHow can we sort multiple columns in a single query?
We can sort multiple columns in a single query by giving more than one column name with ORDER BY Clause. The syntax of the above is as follows −SyntaxSelect Col1, Col2, … from table_name ORDER BY Col1, Col2, …ExampleSuppose we want to sort the table named ‘Student’ by columns ‘Name’ and ‘RollNo’ both then we can write the single query for this as follows −mysql> Select Name, RollNo from student order by name, rollno; +--------+--------+ | name | rollno | +--------+--------+ | Aarav | 150 | | Aryan | 165 ...
Read MoreHow can we amend the declared size of a column's data type in MySQL?
It can be done with the help of ALTER TABLE command of MySQL. Consider the table ‘Student’ in which the size of ‘Grade’ column is declared as Varchar(10), can be seen from the following query −mysql> DESCRIBE Student; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | Name | varchar(20) | YES | | NULL | | | RollNo | int(11) | YES | ...
Read MoreHow can we combine ROW selection with COLUMN selection in MySQL?
For combining ROW selection with COLUMN selection, we can use the ‘WHERE’ clause. For example, we have a table below −mysql> Select * from Student; +--------+--------+--------+ | Name | RollNo | Grade | +--------+--------+--------+ | Gaurav | 100 | B.tech | | Aarav | 150 | M.SC | | Aryan | 165 | M.tech | +--------+--------+--------+ 3 rows in set (0.00 sec)Now, the following query will show how we can combine ROW selection with COLUMN selection using WHERE clause.mysql> Select Name, RollNo, Grade from Student where Grade='M.Sc' or Grade='B.Tech'; +--------+--------+--------+ | Name | RollNo ...
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