MySQL numeric functions

• ABS
• SQRT
• MOD
• CEIL and CEILING
• FLOOR
• RAND
• ROUND
• SIGN
• POW and POWER
• SIN
• ASIN
• COS
• ACOS
• TAN
• ATAN
• COT

MySQL string functions

• LENGTH
• CONCAT
• INSERT
• LOWER
• UPPER
• LEFT
• RIGHT
• TRIM
• REPLACE
• SUBSTRING
• REVERSE

MySQL Date/Time functions

• CURDATE and CURRENT_DATE
• CURTIME and CURRENT_TIME
• NOW and SYSDATE
• UNIX_TIMESTAMP
• FROM_UNIXTIME
• MONTH
• MONTHNAME
• DAYNAME
• DAYOFWEEK
• WEEK
• DAYOFYEAR
• DAYOFMONTH
• YEAR
• TIME_TO_SEC
• SEC_TO_TIME
• DATE_ADD and ADDDATE
• DATE_SUB and SUBDATE
• ADDTIME
• SUBTIME
• DATEDIFF
• DATE_FORMAT
• WEEKDAY

MySQL aggregate functions

• MAX
• MIN
• COUNT
• SUM
• AVG

MySQL flow control functions

• IF
• IFNULL
• CASE

MySQL LEFT Function: Truncate A String From The Left

The LEFT() function in MySQL is used to extract a specified number of characters from the left side of a string. This function can be useful when you need to parse the data in a column that contains text.

Syntax

Here's the basic syntax of the LEFT() function:

LEFT(string, number_of_chars)

• string: This is the original string from which you want to extract characters.
• number_of_chars: This is the number of characters you want to extract from the left side of the string.

Examples

Let's look at a few examples of how to use the LEFT() function.

Example 1:

SELECT LEFT('Hello World', 5);

Output:

'Hello'

In this example, we're extracting the first 5 characters from the string 'Hello World'.

Example 2:

Suppose we have a table named employees with the following data:

And we want to extract the first part of each email address (before the '@' character). We can use the LEFT() function in combination with the LOCATE() function:

SELECT ID, Email, LEFT(Email, LOCATE('@', Email) - 1) as Username
FROM employees;

Output:

In this example, the LOCATE() function is used to find the position of the '@' character in the email address, and then we subtract 1 to get the position of the last character of the username. The LEFT() function then extracts that many characters from the left of the email address.

Note: It's important to note that if the number_of_chars parameter is greater than the length of the string, the LEFT() function will return the whole string. If number_of_chars is negative, the LEFT() function will return an empty string.

1. MySQL SUBSTRING function example:

   • Description: The SUBSTRING function is used to extract a substring from a string in MySQL.
   • Example:

     SELECT SUBSTRING('Hello, World!', 1, 5) AS Result;
     -- Output: Hello
     

2. How to truncate a string from the left in MySQL:

   • Description: Use SUBSTRING to truncate a string from the left.
   • Example:

     SELECT SUBSTRING('Hello, World!', 8) AS Result;
     -- Output: World!
     

3. LEFT vs SUBSTRING in MySQL:

   • Description: LEFT and SUBSTRING are similar, but LEFT is often used for simplicity when truncating from the left.
   • Example using LEFT:

     SELECT LEFT('Hello, World!', 5) AS Result;
     -- Output: Hello
     

4. MySQL RIGHT function for truncating:

   • Description: Use RIGHT to truncate a string from the right.
   • Example:

     SELECT RIGHT('Hello, World!', 6) AS Result;
     -- Output: World!
     

5. Truncate string from the left using MySQL functions:

   • Description: Combine LENGTH and SUBSTRING to truncate from the left.
   • Example:

     SELECT SUBSTRING('Hello, World!', LENGTH('Hello, World!') - 5 + 1) AS Result;
     -- Output: World!
     

6. Substring left side of a string in MySQL:

   • Description: Use SUBSTRING to extract the left side of a string.
   • Example:

     SELECT SUBSTRING('Hello, World!', 1, 7) AS Result;
     -- Output: Hello, 
     

7. MySQL truncate string length from the left:

   • Description: Truncate a string from the left using the length parameter of SUBSTRING.
   • Example:

     SELECT SUBSTRING('Hello, World!', 1, LENGTH('Hello, World!') - 6) AS Result;
     -- Output: Hello
     

8. Using SUBSTRING to cut characters from the left in MySQL:

   • Description: Demonstrate how to cut characters from the left using SUBSTRING.
   • Example:

     SELECT SUBSTRING('MySQL is powerful', 7) AS Result;
     -- Output: is powerful
     

9. Examples of truncating strings in MySQL queries:

   • Description: Various examples demonstrating different ways to truncate strings in MySQL queries.
   • Examples:

     SELECT SUBSTRING('Example 1: Truncate from left', 12) AS Result1,
            SUBSTRING('Example 2: Truncate from right', 1, LENGTH('Example 2: Truncate from right') - 6) AS Result2;
     

10. MySQL string manipulation functions for truncation:

    • Description: Overview of MySQL string manipulation functions like SUBSTRING and LEFT for truncation.
    • Examples:

      SELECT SUBSTRING('MySQL is powerful', 7) AS Result1,
             LEFT('Another example', 8) AS Result2;