Cast to BOOLEAN

The BOOLEAN type represents true or false values, with only two possible states: true value and false value.

FROM String

Behavior Change

Previously, strings like '1.11' could be cast to boolean type 'true', starting from 4.0, they will be converted to null (in non-strict mode) or report an error (in strict mode). Previously, values like 'on', 'off', 'yes', 'no' would be converted to null, starting from 4.0, they can be converted to their corresponding boolean values.

Strict Mode

BNF Definition

<boolean> ::= <whitespace>* <bool_like> <whitespace>*

<bool_like> ::= "0" | "1" | "t" | "T" | "f" | "F" | <yes> | <no> | <on> | <off> | <true> | <false>

<yes> ::= ("y" | "Y") ("e" | "E") ("s" | "S")

<no> ::= ("n" | "N") ("o" | "O")

<on> ::= ("o" | "O") ("n" | "N")

<off> ::= ("o" | "O") ("f" | "F") ("f" | "F")

<true> ::= ("t" | "T") ("r" | "R") ("u" | "U") ("e" | "E")

<false> ::= ("f" | "F") ("a" | "A") ("l" | "L") ("s" | "S") ("e" | "E")

<whitespace> ::= " " | "\t" | "\n" | "\r" | "\f" | "\v"

Rule Description

Boolean values can be in the following forms: 0, 1, yes, no, on, off, true, false, and are case insensitive. Additionally, boolean values can contain any number of whitespace characters before and after (including spaces, tabs, newlines, etc.).

For formats that do not conform, an error is reported.

Examples

String	Cast as bool Result	Comment
"true"	true
"false"	false
" \t\r\n\f\v true \t\r\n\f\v"	true	With leading and trailing whitespace
"1.1"	Error	Invalid format
"YeS"	true	Case insensitive
'+0'	Error	Invalid format

Non-Strict Mode

BNF Definition

<boolean> ::= <whitespace>* <bool_like> <whitespace>*

<bool_like> ::= "0" | "1" | "t" | "T" | "f" | "F" | <yes> | <no> | <on> | <off> | <true> | <false>

<yes> ::= ("y" | "Y") ("e" | "E") ("s" | "S")

<no> ::= ("n" | "N") ("o" | "O")

<on> ::= ("o" | "O") ("n" | "N")

<off> ::= ("o" | "O") ("f" | "F") ("f" | "F")

<true> ::= ("t" | "T") ("r" | "R") ("u" | "U") ("e" | "E")

<false> ::= ("f" | "F") ("a" | "A") ("l" | "L") ("s" | "S") ("e" | "E")

<whitespace> ::= " " | "\t" | "\n" | "\r" | "\f" | "\v"

Rule Description

Boolean values can be in the following forms: 0, 1, yes, no, on, off, true, false, and are case insensitive. Additionally, boolean values can contain any number of whitespace characters before and after (including spaces, tabs, newlines, etc.).

For formats that do not conform, null is returned.

Examples

String	Cast as bool Result	Comment
"true"	true
"false"	false
" \t\r\n\f\v true \t\r\n\f\v"	true	With leading and trailing whitespace
"1.1"	null	Invalid format
"YeS"	true	Case insensitive
'+0'	null	Invalid format

FROM Numeric

Behavior Change

Previously, non-numeric types like date/datetime were allowed to be converted to boolean type, starting from 4.0, this is not supported.

Strict Mode

Rule Description

For numeric types (int/double/decimal), non-zero values are considered true.

Positive and negative zeros in floating point numbers are converted to false.

Examples

Numeric Type	Cast as bool Result	Comment
121231	true
0	false
+0.0	false	Positive zero in floating point
-0.0	false	Negative zero in floating point
-1	true
1	true

Non-Strict Mode

Rule Description

For numeric types (int/double/decimal), non-zero values are considered true.

Positive and negative zeros in floating point numbers are converted to false.

Examples

Numeric Type	Cast as bool Result	Comment
121231	true
0	false
+0.0	false	Positive zero in floating point
-0.0	false	Negative zero in floating point
-1	true
1	true