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MySQL Articles
Page 84 of 355
What is MySQL NULL-safe equal operator and how it is different from comparison operator?
MySQL NULL-safe equal operator, equivalent to standard SQL IS NOT DISTINCT FROM operator, performs an equality comparison like = operator. Its symbol is . It performs differently from the comparison operators in the case when we have NULL as both the operands. Consider the following examples to understand NULL-safe operator along with its difference with comparison operator −mysql> Select 50 50, NULL NULL, 100 NULL; +-----------+---------------+--------------+ | 50 50 | NULL NULL | 100 NULL | +-----------+---------------+--------------+ | 1 | 1 | 0 | +-----------+---------------+--------------+ 1 row in set (0.00 sec) mysql> Select 50 = 50, NULL = NULL, 100 = NULL; +---------+-------------+------------+ | 50 = 50 | NULL = NULL | 100 = NULL | +---------+-------------+------------+ | 1 | NULL | NULL | +---------+-------------+------------+ 1 row in set (0.00 sec)
Read MoreWhat happens if we provide NULL as an argument to MySQL CHAR() function?
MySQL CHAR() function will ignore NULL if it is provided as an argument to it. To understand it, consider the following examples −mysql> Select CHAR(65,66,67,NULL); +---------------------+ | CHAR(65,66,67,NULL) | +---------------------+ | ABC | +---------------------+ 1 row in set (0.00 sec) mysql> Select CHAR(NULL,66,67,NULL); +-----------------------+ | CHAR(NULL,66,67,NULL) | +-----------------------+ | BC | +-----------------------+ 1 row in set (0.00 sec)In both the examples above, CHAR() function ignores the NULL and converts the numeric value into character value.
Read MoreWhat MySQL returns if we provide value larger than 255 as argument to MySQL CHAR() function?
MySQL converts the arguments of CHAR() function which is greater than 255 to multiple result bytes. For example, CHAR(260) is equivalent to CHAR(0,1,0,4). It can be more clear with the help of following statements −mysql> Select HEX(CHAR(256)),HEX(CHAR(1,0)); +----------------+----------------+ | HEX(CHAR(256)) | HEX(CHAR(1,0)) | +----------------+----------------+ | 0100 | 0100 | +----------------+----------------+ 1 row in set (0.00 sec)The above result set shows that CHAR(256) is equivalent to CHAR(1,0).
Read MoreHow can we produce a string, other than default binary string, in a given character set by MySQL CHAR() function?
We can use the keyword USING to produce a string, other than default binary string, in a given character set. Following result set will demonstrate it −mysql> Select CHARSET(CHAR(85 USING utf8)); +------------------------------+ | CHARSET(CHAR(85 USING utf8)) | +------------------------------+ | utf8 | +------------------------------+ 1 row in set (0.00 sec)The above result set shows that the returned binary string is utf8 because we write utf8 after the keyword USING.mysql> Select CHARSET(CHAR(85 USING latin1)); +--------------------------------+ | CHARSET(CHAR(85 USING latin1)) | +--------------------------------+ | latin1 ...
Read MoreIn function INSERT(str, Pos, len, newstr), what would be the result if 'Pos' is not within the length of the string?
MySQL INSERT() function performs no insertion if the position of insertion is not within the length of the string. There are certain cases like we pass a negative or 0(zero) value or the value goes beyond the value of a total number of characters in an original string by 2 when we can say that ‘pos’ is not within the length of the string. It can be understood with the help of the following example −ExampleThe query below will perform no insertion because the ‘pos’ is not within the length of string i.e. a negative value.mysql> Select INSERT('Tutorialspoint', -1, 4, '.com'); +--------------------------------------+ ...
Read MoreIn MySQL, how can we insert a substring at the specified position in a string?
We can use a MySQL INSERT() function to insert a substring at the specified position in a string.SyntaxINSERT(original_string, @pos, @len, new_string)Here, original_string is the string in which we want to insert a new string at the place of some specific number of characters.@pos is the position at which the insertion of the new string should start.@len is the number of characters that should delete from the original string. The starting point of the deletion of characters is the value of @pos.New_string is the string we want to insert into the original string.Examplemysql> Select INSERT('MySQL Tutorial', 7, 8, '@Tutorialspoint'); +------------------------------------------------+ | ...
Read MoreHow can I create a MySQL stored procedure that returns multiple values from a MySQL table?
We can create a stored procedure with both IN and OUT parameters to get multiple values from a MySQL table. To make it understand we are taking an example of a table named ‘student_info’ having the following data −mysql> Select * from student_info; +------+---------+------------+------------+ | id | Name | Address | Subject | +------+---------+------------+------------+ | 101 | YashPal | Amritsar | History | | 105 | Gaurav | Jaipur | Literature | | 110 | Rahul ...
Read MoreHow can user variables be used in MySQL stored procedure?
In MySQL stored procedure, user variables are referenced with an ampersand i.e. @, prefixed to the user variable names. For example, @A, @B, etc. are user variables. To demonstrate it, we are creating the following procedure −mysql> DELIMITER // ; mysql> CREATE PROCEDURE Proc_Uservariables() -> BEGIN -> SET @A = 100; -> SET @B = 500; -> SELECT @A,@B,@A+@B; -> END // Query OK, 0 rows affected (0.00 sec) mysql> Delimiter ; // mysql> CALL Proc_Uservariables(); +------+------+-------+ | @A | @B | @A+@B | +------+------+-------+ | 100 | 500 | 600 | +------+------+-------+ 1 row in set (0.00 sec) Query OK, 0 rows affected (0.01 sec)
Read MoreWhat happens if the argument 'count' in MySQL SUBSTRING_INDEX() function has the value greater than the total number of occurrences of delimiter?
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('My Name is Ram','a',3); +-----------------------------------------+ | SUBSTRING_INDEX('My Name is Ram','a',3) | +-----------------------------------------+ | My Name is Ram | +-----------------------------------------+ 1 row in set (0.00 sec)The above query returns the same string because 3 is greater than the total number of occurrences of delimiter provided as argument i.e. ‘a’. There are only two ‘a’ in the string.
Read MoreWhat are the default rules used by the parser for parsing names of built-in functions?
Actually, when a parser encounters a word that is the name of a built-in function, it must determine whether the name represents a function call or is instead a non-expression reference to an identifier such as a table or column name. consider the following queries −1. Select sum(salary) from employee; 2. Create table sum (i int);In the first query SUM is a reference to a function call and in the second query, it is referencing to table name.Parser follows the following rules to distinguish whether their names are being used as function calls or as identifiers in non-reference context −Rule1 ...
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