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Articles by Lakshmi Srinivas
Page 17 of 24
How can we get some last number of characters from the data stored in a MySQL table's column?
To get some last number of characters from the data stored in MySQL table’s column, we can use MySQL RIGHT() function. It will return the number of characters specified as it argument. We need to provide the name of the column, having the particular record from which we want to get last characters, as its first argument. To demonstrate it we are taking the example of a table named ‘examination_btech’ having the following examination details of students −mysql> Select * from examination_btech; +-----------+----------+--------+ | RollNo | Name | Course | +-----------+----------+--------+ | 201712001 ...
Read MoreHow MySQL evaluates if I try to add two numbers that are contained in quotes?
If we are trying to add two numbers that are contained in quotes, means we are treating the string as a number. In this case, MySQL converts the value into the closet numeric equivalent and evaluates the result. Following example will demonstrate it.Examplemysql> Select '1525' + '200'As Total; +-------+ | Total | +-------+ | 1725 | +-------+ 1 row in set (0.00 sec)
Read MoreWhen MySQL SUBSTRING_INDEX() function returns the same string, provided in the argument, as output?
MySQL SUBSTRING_INDEX() function will return the same string as output if the argument ‘count’ has the value greater than the total number of occurrences of delimiter. It can be demonstrated with the following example −mysql> Select SUBSTRING_INDEX('www.google.co.in','.',4); +-------------------------------------------+ | SUBSTRING_INDEX('www.google.co.in','.',4) | +-------------------------------------------+ | www.google.co.in | +-------------------------------------------+ 1 row in set (0.00 sec)The above query returns the same string because 4 is greater than the total number of occurrences of delimiter provided as argument i.e. ‘.’.
Read MoreHow Are MySQL INSTR() and LIKE operator similar?
We can use both INSTR() function and LIKE operator to search or match a particular pattern and they return same result. It can be demonstrated from the following example of ‘Student’ table.ExampleSuppose we want to search name, which contains ‘av’ in it, from ‘Student’ table. We can use INSTR() function as follows −mysql> Select Name from student where INSTR(name, 'av') > 0; +--------+ | Name | +--------+ | Gaurav | | Aarav | | Gaurav | +--------+ 3 rows in set (0.00 sec)Now, for the same kind of search we can use LIKE operator as follows −mysql> Select Name ...
Read MoreHow can we delete multiple rows from a MySQL table?
We can use DELETE statement along with a WHERE clause, which identifies those multiple rows, to delete multiple rows from MySQL table.Examplemysql> Select * from names; +------+-----------+ | id | name | +------+-----------+ | 1 | Rahul | | 2 | Gaurav | | 3 | Raman | | 5 | Ram | +------+-----------+ 4 rows in set (0.00 sec) mysql> DELETE from names WHERE id > 2; Query OK, 2 rows affected (0.04 sec)The query above will delete multiple rows because WHERE clause identify two rows having id > 2 from table ‘names’.mysql> Select * from names; +------+-----------+ | id | name | +------+-----------+ | 1 | Rahul | | 2 | Gaurav | +------+-----------+ 2 rows in set (0.00 sec)
Read MoreWhat are the different ways to maintain data integrity in child table when the record is deleted in parent table?
When two tables are connected with Foreign key and data in the parent table is deleted, for which record exists in child table too, then followings are the ways to maintain data integrity −On Delete CascadeThis option will remove the record from child table too if that value of the foreign key is deleted from the main table.On Delete Null This option will set all the values in that record of child table as NULL, for which the value of the foreign key is deleted from the main table.
Read MoreHow can we remove NOT NULL constraint from a column of an existing MySQL table?
We can remove a NOT NULL constraint from a column of an existing table by using the ALTER TABLE statement.ExampleSuppose we have a table ‘test123’ having a NOT NULL constraint on column ‘ID’ as follows −mysql> DESCRIBE test123; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | ID | int(11) | NO | | NULL | | | Date | date | YES | | NULL | | +-------+---------+------+-----+---------+-------+ 2 rows in set (0.04 sec)Now if we ...
Read MoreHow to Calculate the Area of a Triangle using Python?
Calculating the area of a triangle is a formula that you can easily implement in python. If you have the base and height of the triangle, you can use the following code to get the area of the triangle,def get_area(base, height): return 0.5 * base * height print(get_area(10, 15))This will give the output:75If you have the sides of the triangle, you can use herons formula to get the area. For example,def get_area(a, b, c): s = (a+b+c)/2 return (s*(s-a)*(s-b)*(s-c)) ** 0.5 print(get_area(10, 15, 10))This will give the output:49.607837082461074
Read MoreHow do I run two python loops concurrently?
You will need to use a multiprocessing library. You will need to spawn a new process and provide the code to it as an argument. For example,from multiprocessing import Processdef loop_a(): for i in range(5): print("a") def loop_b(): for i in range(5): print("b") Process(target=loop_a).start() Process(target=loop_b).start()This might process different outputs at different times. This is because we don't know which print will be executed when.
Read MoreHow to write inline if statement for print in Python?
Python provides two ways to write inline if statements. These are:1. if condition: statement2. s1 if condition else s2Note that second type of if cannot be used without an else. Now you can use these inline in a print statement as well. For example,a = True if a: print("Hello")This will give the output:Helloa = False print("True" if a else "False")This will give the output:False
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