Show <=>Syntax<=> DescriptionNULL-safe equal operator. It performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL.
When used in row comparisons these two queries return the same results: SELECT (t1.a, t1.b) <=> (t2.x, t2.y) FROM t1 INNER JOIN t2; SELECT (t1.a <=> t2.x) AND (t1.b <=> t2.y) FROM t1 INNER JOIN t2; See also NULL Values in MariaDB. ExamplesSELECT 1 <=> 1, NULL <=> NULL, 1 <=> NULL; +---------+---------------+------------+ | 1 <=> 1 | NULL <=> NULL | 1 <=> NULL | +---------+---------------+------------+ | 1 | 1 | 0 | +---------+---------------+------------+ SELECT 1 = 1, NULL = NULL, 1 = NULL; +-------+-------------+----------+ | 1 = 1 | NULL = NULL | 1 = NULL | +-------+-------------+----------+ | 1 | NULL | NULL | +-------+-------------+----------+
CommentsContent reproduced on this site is the property of its respective owners, and this content is not reviewed in advance by MariaDB. The views, information and opinions expressed by this content do not necessarily represent those of MariaDB or any other party. I have an update query that updates a field in one table when the value does not match a field in another table.
The problem I am having is that it is not picking up when a.field1 is null and b.field3 is a value OR if a.field1 is a value and b.field3 is null. I have gotten around this by adding the following...
My question is more centered around why this is happening and how to best structure the query in order to prevent this? asked Apr 10, 2013 at 14:52
HeatherHeather 1911 gold badge1 silver badge4 bronze badges 3 The problem is with NULL comparison. If a.field1 or b.field3 is NULL you need to use a IS NULL or IS NOT NULL statement. You could use a default value for a.field1 and b.field3 with the ISNULL function.
in this case there is a comparison with the value 0.
Dale K 23.9k15 gold badges42 silver badges71 bronze badges answered Apr 10, 2013 at 15:00
10 The result of comparing anything to NULL, even itself, is always NULL(not TRUE or FALSE). Use option with EXISTS and EXCEPT operators.
answered Apr 10, 2013 at 15:07
1 In addition to handling the NULL logic correctly, you need to enclose multiple conditions that are to be applied together in parentheses. Something like this (not sure I understood your conditions exactly).
answered Apr 10, 2013 at 14:58
DOKDOK 32.1k7 gold badges60 silver badges92 bronze badges 1 Tim Shmelter is right in his comment, This means, even if I think the solution here does not lie in the answered Apr 10, 2013 at 15:00
RachchaRachcha 8,3168 gold badges47 silver badges70 bronze badges 3 You can use
I've assumed that your type is number, though you can use other data types. I've also assumed that if both values are NULL then the two rows are equivalent.
Dale K 23.9k15 gold badges42 silver badges71 bronze badges answered Apr 16, 2015 at 14:20
ChanochChanoch 5637 silver badges16 bronze badges When you write in your query answered Apr 10, 2013 at 15:04
0 This will check if the Column1 and Column2 is equal, Additionally used Convertion to VARBINARY to compare in case sensitive and you can remove it if not necessary.
You can change the end of expression to Hope this help. answered Dec 1, 2014 at 23:00
QMasterQMaster 3,6163 gold badges42 silver badges56 bronze badges Another way would be to use CHECKSUM function
answered Mar 17, 2016 at 18:56
Captain O.Captain O. 3831 silver badge9 bronze badges Which operator is used to compare the NULL value in SQL?The IS NULL operator is used to test for empty values (NULL values).
Can we compare 2 NULL values in SQL?Comparing NULL values
Since you can't use a equality operator in the WHERE clause (remember, NULL values can't be equated or compared), the right way to compare NULL values is to use the IS and IS NOT operators.
Which operator is used to compare the equal values in SQL?Output: Demonstration of various Comparison Operators in SQL: Equal to (=) Operator: It returns the rows/tuples which have the value of the attribute equal to the given value.
Is != And same in SQL?If != and <> both are the same, which one should be used in SQL queries? Here is the answer – You can use either != or <> both in your queries as both technically same but I prefer to use <> as that is SQL-92 standard.
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