Returns 1 true if expr is equal to any of the values in the IN list, else returns 0 false. Type conversion takes place according to the rules described in Section If no type conversion is needed for the values in the IN list, they are all non- JSON constants of the same type, and expr can be compared to each of them as a value of the same type possibly after type conversion , an optimization takes place.
The values the list are sorted and the search for expr is done using a binary search, which makes the IN operation very quick. IN can be used to compare row constructors:. You should never mix quoted and unquoted values in an IN list because the comparison rules for quoted values such as strings and unquoted values such as numbers differ.
Mixing types may therefore lead to inconsistent results. For example, do not write an IN expression like this:. In both cases, the comparison values are converted to floating-point values, yielding 0. IN syntax can also be used to write certain types of subqueries. All arguments are treated as integers. This is because a binary search is used very fast.
For details, including the return value after a multiple-row insert, see Section See Section 5. LEAST value1 , value2 , With two or more arguments, returns the smallest minimum-valued argument. The arguments are compared using the following rules:.
No comparison is needed. If all arguments are integer-valued, they are compared as integers. If at least one argument is double precision, they are compared as double-precision values.
If the arguments comprise a mix of numbers and strings, they are compared as strings. Beispiel 1 Boolesche und null-Vergleiche. Beispiel 2 Umschreibung von Standard-Array-Vergleichen. Aufgrund der Art wie Gleitkommazahlen float intern dargestellt werden, sollten zwei Gleitkommazahlen nicht auf Gleichheit getestet werden. Weitere Informationen sind der Dokumantation von float zu entnehmen. Ein weiterer Vergleichs-Operator ist der "? Beispiel 3 Zuweisen eines Standardwerts. Der Ausdruck ausdr1?
Seit PHP 8. Weiterhin gibt es den "?? Beispiel 5 Zuweisung eines Standardwerts. Insbesondere gibt dieser Operator keinen Hinweis und keine Warnung aus, wenn der Wert auf der linken Seite nicht existiert, genau wie isset. Hinweis : Es ist zu beachten, dass der null-Coalescing-Operator ein Ausdruck ist und nicht als Variable, sondern als Wert eines Ausdrucks ausgewertet wird. Hinweis : Es ist zu beachten, dass der null-Coalescing-Operator einfach verschachtelt werden kann: Beispiel 6 Verschachtelung des null-Coalescing-Operators.
Operator zur Fehlerkontrolle ». Submit a Pull Request Report a Bug. Vergleichs-Operatoren Vergleichs-Operatoren erlauben es — wie der Name schon sagt — zwei Werte zu vergleichen. Submit a Pull Request Report a Bug. Comparison Operators Comparison operators, as their name implies, allow you to compare two values. Warning Prior to PHP 8. Warning Comparison of floating point numbers Because of the way float s are represented internally, you should not test two float s for equality.
See Also strcasecmp strcmp Array operators Types. Ternary Operator Another conditional operator is the "? Null Coalescing Operator Further exists the "?? I use strcmp now for string comparison Of course, this could be overcome by suppressing the notice using the operator. For instance Stick with strict comparisons Be careful when using the ternary operator! So, if you think to mix more sentences with the?
Be aware that the null coalesce operator?? The following contrasts the trinary operator associativity in PHP and Java. Beware of the consequences of comparing strings to numbers. You can disprove the laws of the universe. This stems from the use of the UNIX function strtod to convert strings to numbers before comparing. This is more complicated when you have multi-dimensional arrays. Rizier 57k 16 16 gold badges 88 88 silver badges bronze badges. That's easy to cast. All other values though have, for all practical purposes, virtually unlimited combinations.
Raithlin, careful of array. Raithlin, Many many more gotchas. In JavaScript: ""! Show 9 more comments. Patrick Glandien Patrick Glandien 7, 5 5 gold badges 38 38 silver badges 47 47 bronze badges.
If it was just comparing the types it would just be called a "type comparison" wouldn't it. Show 3 more comments. Hope: If you are using PHP, Thou shalt not use the double equals operator because if you use triple equals, the only edge cases to worry about are NAN and numbers so close to their datatype's maximum value, that they are cast to infinity. Eric Leschinski Eric Leschinski k 87 87 gold badges silver badges bronze badges.
Is it really a good idea also secure to always use triple equals? Yes, the transitive property of triple equals makes it more secure and webscale. How can a number be close to infinity? Notably 1. JavaScript does not has this problem because there is only one numeric type though has other problems like integer rounding because of it. For example, the sample below will display 'x and y are equal', but not 'x and y are identical'.
Peter Mortensen DavidThomas It's not exactly the same. See stackoverflow. I have DV'ed this answer because it came 30 minutes after the OP's self-answer detailed the same insight regarding loosely typed comparisons. This javascript answer to an originally and currently php-tagged question really should be removed, but to do so the vote tally will need to come down via community effort.
In other words, many more DVs are necessary for appropriate curation to take place and remove this deleted user's answer. It's all about data types. Why would you need this?
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