DEV Community: Rahul Pratap Singh

TYPES OF ERRORS IN PROGRAMMING LANGUAGE.

Rahul Pratap Singh — Sat, 25 Feb 2023 18:17:31 +0000

😎🙌Greetings! 😎😎✨ As we delve into the realm of coding🐱‍🐉🐱‍🚀, we often encounter a variety of errors👀🤦‍♂️, be it in our personal projects or in the corporate world. Even as beginners, it is essential for us to foster our curiosity about these common errors that we encounter on a daily basis, in order to gain a deeper understanding of programming skills.

Well, there are several errors😢😢 you might face while coding. Still, I would like to share 4 common types of error which are generally encountered by us & should be well known by a programmer & a newbie in-order to debug it quickly to produce more effective & efficient code😃😃.

I'm going to break down these 4 errors in straightforward steps by providing a clear & simple explanation😎🙌 with a small code snippet for reference purposes.

COMPILATION ERROR -> Compilation errors generally occur due to mistakes in the "syntax" of the programming language.

When the programmer by mistake has left the semicolon (;) or has mistyped any keyword which is not accepted by the grammar(rules) of that specific programming language, we term it as a compilation error. It is relatively easy to fix.

We can also call it "syntax error" in simple words.

Here, the programmer has mistyped the "println" keyword to "printnl" which is against the grammar(rules) of the programming language (here, I'm using JAVA), which will give the output.

Here, the compiler throws the "compilation(syntax) error".
It can be fixed simply by changing the keyword to "println".

2.RUN-TIME ERROR -> Run-time errors are some of the exceptional types of errors where your code tries to perform or access such operations which are not allowed by the programming language.
The best examples are:

               - Dividing a number by zero (0), which will 
                 simply throw, "ArithmeticException".

               - Accessing a memory location that is not 
                 allocated, which will 
                 simply throw, 
                 "ArrayIndexOutOfBoundsException".

Here, the compiler throws the "run-time error".

It can be fixed simply by accessing the location that is under the scope of an array.

              - Invalid input in Java can cause a runtime 
                error when the program is expecting certain 
                types of input, but the input provided by the 
                user is not valid.

3.TIME-LIMIT EXCEEDED -> This error is generally thrown by the compiler when your code runs or executes an infinite number of times (goes into an infinite loop). The program will never finish its execution, eventually encountering a "Time Limit Exceeded" error.

We can fix it by adding a counter variable that counts the number of iterations and exits the loop when it reaches a particular value (say 10), You can also use a condition that depends on the programmer's input.

It will throw the "Time Limit Exceeded" error.

4.*SEGMENTATION FAULT *-> This error occurs when your code tries to access memory that it is not allowed to access by it.
The segmentation error is also one of the runtime errors, so what's the difference peeps👀😒?

In simple words😃 a segmentation fault is a specific type of runtime error that occurs when a program tries to access memory it is not allowed to access, while a runtime error is a more general term that encompasses a wide range of errors that can occur during program execution like - division by zero, array out-of-bounds access.

A segmentation fault will lead to a crash of your program in most cases🤷‍♂️🤷‍♂️ (logs of this fault(error) are recorded in the file named "CORE DUMPS" with an extension- .dmp extension).

I hope😎🙌 this post helps the budding developer community & newbies who want to delve into errors in their code & saves their time by spotting them easily.😃💖✨😎

Thank You!!!

SQL commands types with examples

Rahul Pratap Singh — Sun, 19 Feb 2023 17:45:16 +0000

Hello Folks😎, this is my first post✌.

Just for fun, I would like to share with you all the SQL command types with their examples.

*## What is SQL? *

1- The SQL language is one of the primary reasons for the success of relational databases in the corporate world.
Because it became a standard for relational
databases for executing queries & fetching data.

2 - SQL uses some of the technical jargon like table, row(tuple), column(attribute) & schema.

3 - A SQL table is the basic element of a relational database (RDS).

What are SQL commands?

Structured query language (SQL) commands are specific keywords or SQL statements that developers use to manipulate the data stored in a relational database. We can categorize SQL commands in 5 different ways.

a -> DDL = DDL, which stands for "Data Definition Language", which is generally responsible for the structure of the relation(table), we can also call it a "paper schema".
We can design our database through the following commands in SQL.

CREATE -> Used to create the table(schema). Creation of new
table requires you to specify the table name
columns & the data type of each column.
```
       Syntax: CREATE TABLE TABLE_NAME (COLUMN_NAME 
               DATATYPES[,....]); 
```
DROP -> The DROP command can be used to drop named
schema(table) elements, such as tables domains, or
constraints. In layman's terms, it will delete the
whole table along with the data stored inside it.
```
        Syntax: DROP TABLE table_name;  
```
ALTER -> The ALTER command allows you to add/delete or modify
the columns(attributes) to an existing table in the
database.
```
        Syntax: ALTER TABLE table_name ADD column_name 
                COLUMN-definition;   
```
TRUNCATE -> The TRUNCATE command simply deletes the whole
contents of the selected existing
table. But it will not delete the table itself,
only the data inside it, will be deleted.
```
         Syntax: TRUNCATE TABLE table_name;  
```
COMMENT -> The COMMENT command helps the developer to add
extra information about their SQL queries, you can
include a comment in a statement that describes
the purpose of the statement within your
application.
Begin the comment with a slash and an asterisk
(/) write your text or comment. End the comment
with an asterisk and a slash (/).
- RENAME -> There are some situations where we need to change
  the name of the table/ columns or rows. The
  The "RENAME" command is used to rename the
  existing table/columns or the rows of a table.
```
     Syntax: RENAME old_table _name To new_table_name;  
```

b ->** DQL = DQL, stands for "DATA QUERY LANGUAGE". DQL
consists of instructions, used to fetch data from
the database. The DQL only uses the "SELECT"
command.

- SELECT -> It is the most frequently used SQL command, used 
            to select the data from a database. The result or 
            records after executing the query will be stored 
            in a result-set table.

            Syntax: SELECT column1, column2, ...
                    FROM table_name;
            If you want to select all the fields at, once use 
            (*) asterisk.

            Syntax: SELECT * FROM table_name;

c ->** DML = DML, stands for "DATA MANIPULATION LANGUAGE".
DML is used to modify or bring some changes in the
existing database table. We can update the new
information or modify existing database records in
the table.
The changes made here are not automatically
saved, it can be rollback when needed.
We can modify or update our database through the
following commands in SQL.

INSERT -> This command is used to insert new records in the
database table.
```
       We can insert the data in two ways-
       a - By specifying column names (You don't need to 
           specify the column name where the data will be 
           inserted, you need only their values.)

           Syntax: INSERT INTO TABLE_NAME    
                   (col1, col2, col3,... col N)  
                   VALUES (value1, value2,..valueN);

       b - Without specifying column names (The second 
           the method needs us to specify both the column 
           name and values that you want to insert.)

             Syntax: INSERT INTO TABLE_NAME    
                     VALUES (value1, value2,...valueN);   
```
- UPDATE -> This command is used to update or change the row or
  column value of the table.
```
  Syntax: UPDATE table_name SET [column_name1= 
          value1,column_nameN = valueN] [WHERE 
          CONDITION]   
```
- DELETE -> This command is used to delete one or more
  records(rows) from the database table.
```
  Syntax: DELETE FROM table_name [WHERE condition];
```
- LOCK -> The command is used to gain Exclusive(X) or
  Shared(S) lock on the specified table. This lock
  persists until the end of the transaction.
```
  Syntax: LOCK TABLE table-Name IN {SHARE | EXCLUSIVE 
          MODE}
```
- MERGE -> The "MERGE" command is popularly used to
  perform the insert, update & delete operation just
  in a single go. No need to write separate logic
  for each of the operations.
```
   Syntax: 
          MERGE target_table USING source_table
          ON merge_condition
          WHEN MATCHED
          THEN update_statement
          WHEN NOT MATCHED
          THEN insert_statement
          WHEN NOT MATCHED BY SOURCE
          THEN DELETE;
```
d ->** DCL = "DCL", stands for "DATA CONTROL LANGUAGE". This
command generally deals with the permission &
rights of a user.
The Database Administrator (DBA) uses the data
control language (DCL) to manage or authorize
the database access for other users in the table.
We can grant or revoke the permissions in the

database through the following commands in SQL.
- GRANT -> "GRANT" command is used to give access &
  privilege to the user, by which he/she can make
  some changes in the table.
```
     Syntax: GRANT SELECT, UPDATE ON MY_TABLE TO 
             SOME_USER, ANOTHER_USER;  
```
- REVOKE -> "REVOKE" command is used to withdraw user access &
  
  the privilege of the user.
```
     Syntax: REVOKE SELECT, UPDATE ON MY_TABLE FROM 
             USER1, USER2;  
```
e ->** TCL = "TCL" stands for "TRANSACTION CONTROL LANGUAGE".
Consecutive, Read/Write operations in the
database is called "TRANSACTION".
It is used to manage our transactions so that we
can be sure that it is successfully carried out
& has not violated the integrity of the
database.
The following commands come under the TCL are:
COMMIT -> "COMMIT", command is generally used to save all
the transaction to a database, after performing
all the operations on it.
```
           Syntax: COMMIT; 
```
- ROLLBACK -> "ROLLBACK", command is used to undo all the
  transactions(operations) that have not already
  been saved(committed) to the database.
```
       Syntax: ROLLBACK; 
```
- SAVEPOINTS -> "SAVEPOINTS", command works like a marker, used
  to roll the transaction back to a certain point
  
  without rolling back the entire transaction.
```
       Syntax: SAVEPOINT SAVEPOINT_NAME; 
```

I hope you've enjoyed😎😎 this simple post on SQL commands.
Thank You! 👍

DEV Community: Rahul Pratap Singh

TYPES OF ERRORS IN PROGRAMMING LANGUAGE.

SQL commands types with examples

*What are SQL commands? *

What are SQL commands?