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What is the difference between <> and != operators in MySQL? [duplicate]
(4 answers)
Closed 7 years ago.
Why are there two negation operators in SQL language? != and <>.
Are they redundant or is there a difference between them depending on operands ?
Which one should I use to negate strings in MySQL ?
<> is ISO Sql Standard
!= is vendor specific
They both have no difference among them. It is just a personal preference which one to use. I always prefer <> since it is a ISO SQL standard
The SQL standard only specifies <> for not equals. SQL:2011 Foundation, section 5.2 <token> and <separator> specifies:
<not equals operator> ::=
<>
However some SQL implementations (like MySQL) also support != as a lot of programmers are more familiar with != for not equals. They are fully equivalent, so you can use either, but from a standards point of view you should use <>.
See also the MySQL documentation for not equals.
Related
This question already has answers here:
Should I use != or <> for not equal in T-SQL?
(14 answers)
Closed 8 years ago.
I just wanted to know if there is a difference between <> and != when expressing inequality in SQL queries.
Technically these both function are the same, so you may choose whichever you find more readable.
The duplicate question has a relevant line:
'<>' is from the SQL-92 standard, '!=' is a proprietary T-SQL
operator.
Also to note that there are may database which doesnot != but since you have tagged it as SQL Server then there is no differenc between them
Recently I's learning Hibernate by reading its official guide document, Today I get confused when studying the chapter 'Expressions', all examples in document use '<>' expression to check it 2 columns are equal instead of '!=', so I want to ask question what is the difference between '<>' and '!='? and what advantage does '<>' have?
Thanks so much.
No difference.
The SQL standard is actually <> for "not equals", but (virtually?) every database allows != as a synonymous operator, because most application languages use !=. Hibernate allows it too.
<> and = are opposites -- <> refers to Not Equal.
I would like to know if there are any differences in between the two not equal operators <> and != in Oracle.
Are there cases where they can give different results or different performance?
No there is no difference at all in functionality.
(The same is true for all other DBMS - most of them support both styles):
Here is the current SQL reference: https://docs.oracle.com/database/121/SQLRF/conditions002.htm#CJAGAABC
The SQL standard only defines a single operator for "not equals" and that is <>
Actually, there are four forms of this operator:
<>
!=
^=
and even
¬= -- worked on some obscure platforms in the dark ages
which are the same, but treated differently when a verbatim match is required (stored outlines or cached queries).
At university we were taught 'best practice' was to use != when working for employers, though all the operators above have the same functionality.
According to this article, != performs faster
http://www.dba-oracle.com/t_not_equal_operator.htm
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Speed difference between If-Else and Ternary operator in C…?
This is a very simple question, does the ternary operator increase the speed of execution in comparison to if else statement?
No. Most languages parse it to a very similar syntax tree. Any jit/optimizer is going to collapse it into 'basic blocks' of simple instructions without jumps; and from that point on it will optimize the same.
There could, of course, be some really bad systems out there for which this is not true; but gcc/msvc/c# will all deal with it equally well.
It's abundance can usually be associated with the fact that it is an expression instead of just a logic statement. This makes it all to easy to do things like (note: really ugly example ahead):
size_t n = strlen( pszVar == NULL ? "" : pszVar );
I was wondering why MYSQL uses a single equals sign in conditional statements instead of the more typical two equals signs. Is there a technical/historical reason for this? Thanks.
Hi, I was wondering why MYSQL uses a single equals sign in conditional statements instead of the more typical two equals signs. Is there a technical/historical reason for this? Thanks.
Comparison is much more common in SQL than assignment.
That's why SQL uses more short syntax to do more common things.
In classical SQL, comparison can be distinguished from assignment by context (assignment can be only in SET clause of an UPDATE statement), that's why one operator can be used for both operations.
In MySQL's extension to SQL, assignment to a session variable is denoted by :=
More like historical.
It's SQL. It has used a single equals sign for comparison since the early '70s.
There is never a case for ambiguity in SQL.
In the original A Guide to the SQL Standard by C.J.Date (1987 edition), = for assignment is only used in the SET clause of UPDATE. Everywhere else = is used it is used for comparison.
But in other languages, such as C/C++/C#/Java, = can be used as assignment but it also returns a value. So a = b means "set a equal to b, and return a" whereas a == b means "return true if a and b are equal". (This leads to a very common bug in C programs, because if (a = b) and if (a == b) are both valid, since the result doesn't have to be a bool.)
Some languages like JavaScript/ECMAScript also introduce === as a third type of comparison. In those languages, == means "convert to same type and compare" whereas === means "return true only if they are the same type and same value."