![]() ![]() Notice that BETWEEN treats the endpoint values as included in the range. The BETWEEN predicate simplifies range tests: a BETWEEN x AND y NULL::boolean IS NOT UNKNOWN → f (rather than NULL) Test whether boolean expression yields true or false. NULL::boolean IS UNKNOWN → t (rather than NULL) Test whether boolean expression yields unknown. NULL::boolean IS NOT FALSE → t (rather than NULL) Test whether boolean expression yields true or unknown. NULL::boolean IS FALSE → f (rather than NULL) ![]() Test whether boolean expression yields false. NULL::boolean IS NOT TRUE → t (rather than NULL) Test whether boolean expression yields false or unknown. NULL::boolean IS TRUE → f (rather than NULL) Test whether boolean expression yields true. Test whether value is not null (nonstandard syntax). Test whether value is null (nonstandard syntax). NULL IS NOT DISTINCT FROM NULL → t (rather than NULL) NULL IS DISTINCT FROM NULL → f (rather than NULL)ĭatatype IS NOT DISTINCT FROM datatype → booleanĮqual, treating null as a comparable value.ġ IS NOT DISTINCT FROM NULL → f (rather than NULL) Not equal, treating null as a comparable value.ġ IS DISTINCT FROM NULL → t (rather than NULL) Not between, after sorting the two endpoint values.ĭatatype IS DISTINCT FROM datatype → boolean These behave much like operators, but have special syntax mandated by the SQL standard.ĭatatype BETWEEN datatype AND datatype → booleanīetween (inclusive of the range endpoints).ĭatatype NOT BETWEEN datatype AND datatype → booleanĭatatype BETWEEN SYMMETRIC datatype AND datatype → booleanīetween, after sorting the two endpoint values.ĭatatype NOT BETWEEN SYMMETRIC datatype AND datatype → boolean There are also some comparison predicates, as shown in Table 9.2. Use the BETWEEN predicates shown below to perform range tests. Thus, expressions like 1 < 2 < 3 are not valid (because there is no < operator to compare a Boolean value with 3). Some cases of this sort are implemented directly by “ cross-type” comparison operators, but if no such operator is available, the parser will coerce the less-general type to the more-general type and apply the latter's comparison operator.Īs shown above, all comparison operators are binary operators that return values of type boolean. It is usually possible to compare values of related data types as well for example integer > bigint will work. In addition, arrays, composite types, and ranges can be compared if their component data types are comparable. These comparison operators are available for all built-in data types that have a natural ordering, including numeric, string, and date/time types. Hence, it is not possible to implement != and operators that do different things. != is an alias, which is converted to at a very early stage of parsing. Similarly, you cannot add a number to a time, only another time.Is the standard SQL notation for “ not equal”. For example, you cannot subtract a string from a number or a date. With the exception of integer and float, types can not be mixed in an operation. You can use brackets to change the sequence in which the operation is evaluated: If priorities are equal, the operation is evaluated from left to right: If an operation contains more than one operator, then the operators are evaluated according to the priorities listed in the tabel above, with the highest priority being evaluated first. This means that the operand to the right of the operator will only be evaluated if the result of the conjunction can still change.Īpart from !, ~, ||, and &, the operators can also be combined with an assignment. The logical conjunctions AND and OR are excluding. They require two operands, one to the left and one to the right of the operator. They have only one operand and this must be to the right of the operator. Logical AND, applicable to the type boolean Logical OR, applicable to the type boolean Greater than or equal to, applicable to the types integer, float, time and string Less than or equal to, applicable to the types integer, float, time and string Greater than, applicable to the types integer, float, time and string Less than, applicable to the types integer, float, time and string Subtraction, applicable to the types integer, float and timeīitwise shift to the left, applicable to the type integerīitwise shift to the right, applicable to the type integerīitwise OR, applicable to the type integerīitwise AND, applicable to the type integerīitwise exclusive OR, applicable to the type integer Modulo (to make remainder), applicable to the type integerĪddition, applicable to the types integer, float, time and string Multiplication, applicable to the types integer and floatĭivision, applicable to the types integer and float Logical Negation, applicable to the type booleanīinary Negation, applicable to the type integer ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |