Allow casting of integers 0/1 to new boolean data type false/true
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Key: CORE-3849
URL: http://tracker.firebirdsql.org/browse/CORE-3849
Project: Firebird Core
Issue Type: Improvement
Components: Engine
Affects Versions: 3.0 Initial
Reporter: lacak
Priority: Minor
AFAIK current implementation allows casting of character strings 'false' /
'true' to boolean values false / true.
(it is compliant with sql standard)
It will be nice if there will be supported also casting from 0 / 1 to false /
true like it is supported in other RDBMSs
(it will increase cross database portability and compatibility with others
RDBMSs where exists native BOOLEAN data type or where is "emulated" using
other data types like MSSQL: BIT (0/1) or MySQL:BOOL (synonym for TINYINT))
Here are some examples why 0/1 :
PostgreSQL: http://www.postgresql.org/docs/9.0/interactive/datatype-boolean.html
Ingres: "Boolean columns accept as input the literal values FALSE and TRUE, 0
and 1 (which correspond to false and true, respectively), and the strings
'FALSE' and 'TRUE'." ... "CAST(integer AS BOOLEAN) is accepted for values 0 and
1."
MySQL: "However, the values TRUE and FALSE are merely aliases for 1 and 0"
http://dev.mysql.com/doc/refman/5.5/en/numeric-type-overview.html
>From sql standard:
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"In comparisons of boolean values, True is greater than False"
(from subclause 13.4 Calls to an <externally-invoked procedure>)
"If the caller language of EP is C, then a reference to PN that assigns the
value False to PN implicitly assigns the value 0 (zero) to PI; a reference to
PN that assigns the value True implicitly assigns the value 1 (one) to PI."
>From programing languages world:
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in C99 standard (ISO/IEC 9899) is _Bool :
"An object declared as type _Bool is large enough to store the values 0 and 1."
"true which expands to the integer constant 1, false which expands to the
integer constant 0"
in C++ (ISO/IEC 14882) is Bool:
"An rvalue of type bool can be converted to an rvalue of type int, with false
becoming zero and true becoming one."
"If the source type is bool, the value false is converted to zero and the value
true is converted to one."
in Pascal (ISO/IEC 10206:1990):
"The ordinal numbers of the truth values denoted by false and true shall be the
integer values 0 and 1 respectively."
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