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As we know that in MySQL by default || operator is a logical OR operator but it depends upon PIPES_AS_CONCAT SQL mode. If PIPES_AS_CONCAT SQL mode is enabled, then || operator works as string concatenation. At that time its precedence would be between ^ and the unary operator. Following example will make it understand −mysql> Set @C='tutorials'; Query OK, 0 rows affected (0.00 sec) mysql> Set @D='point'; Query OK, 0 rows affected (0.00 sec) mysql> Select @C||@D; +--------+ | @C||@D | +--------+ | 1 | +--------+ 1 row in set (0.00 sec)The result set of the ... Read More
In MySQL, basically the precedence of ! operator in comparison with NOT operator depends upon the enabling or disabling of HIGH_NOT_PRECEDENCE SQL mode as follows −Disabled HIGH_NOT_PRECEDENCE SQL − In this case,! the operator has higher precedence than NOT operator.Enabled HIGH_NOT_PRECEDENCE SQL − In this case,! the operator has the same precedence as NOT operator.
For combining values of two or more columns, we can use MySQL CONCAT() function. In this case, the arguments of the CONCAT() functions would be the name of the columns. For example, suppose we have a table named ‘Student’ and we want the name and address of the student collectively in one column then the following query can be written −mysql> Select Id, Name, Address, CONCAT(ID, ', ', Name, ', ', Address)AS 'ID, Name, Address' from Student; +------+---------+---------+--------------------+ | Id | Name | Address | ID, Name, Address | +------+---------+---------+--------------------+ | 1 | Gaurav | Delhi ... Read More
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)
When we use NULL-safe operator with row comparisons like (A, B) (C, D) then its performance is equivalent to (A C) AND (B D). Following example will demonstrate it −mysql> Select (100,50) (50,100); +-----------------------+ | (100,50) (50,100) | +-----------------------+ | 0 | +-----------------------+ 1 row in set (0.00 sec) mysql> Select (100,50) (100,50); +-----------------------+ | (100,50) (100,50) | +-----------------------+ | 1 | +-----------------------+ 1 row in set (0.00 sec)The above result sets show how NULL-safe operators can be used with row comparison.
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.
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).
Actually, the CASE statement has the functionality of an IF-THEN-ELSE statement. It has the following syntax −CASE WHEN condition_1 THEN {...statements to execute when condition_1 is TRUE...} [ WHEN condition_2 THEN {...statements to execute when condition_2 is TRUE...} ] [ WHEN condition_n THEN {...statements to execute when condition_n is TRUE...} ] [ ELSE {...statements to execute when all conditions were FALSE...} ] END CASE;The CASE statement will execute the ELSE clause if none of the WHEN clauses were executed.To demonstrate the use of CASE statement within MySQL stored procedure, we are creating the following stored procedure which ... Read More
As we know that MySQL provides us loop statements that allow us to execute a block of SQL code repeatedly based on a condition. WHILE loop statement is one of such kind of loop statements. Its syntax is as follows −WHILE expression DO statements END WHILEActually, the WHILE loop checks the expression at the starting of every iteration. If the expression evaluates to true, MySQL will execute statements between WHILE and END WHILE until the expression evaluates to false. The WHILE loop checks the expression before the statements execute, that is why it is also called the pretest loop.To demonstrate ... Read More
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 More