IS_TRUE Function

is_true(expr)

Description

The IS_TRUE function determines whether the value of an expression is true. This function supports boolean and string types, and can recognize various string formats that represent true.

Parameters

• expr: BOOLEAN or STRING type, the expression to evaluate.

Return Type

• Returns BOOLEAN type.
• Returns true if the expression value is true or a string representing true.
• Returns false if the expression value is false or a string representing false.
• Returns false if the expression value is NULL.

Notes

• The IS_TRUE function recognizes the following strings as true: 't', 'true', '1', 'yes'.
• The IS_TRUE function recognizes the following strings as false: 'f', 'false', '0', 'no'.
• Difference from using expr directly: is_true(NULL) returns false, while NULL in a boolean context is handled specially.
• String matching is case-insensitive.

Examples

1. Boolean evaluation

SELECT is_true(true), is_true(false), is_true(NULL);
+---------------+----------------+----------------+
| is_true(true) | is_true(false) | is_true(NULL)  |
+---------------+----------------+----------------+
| true          | false          | false          |
+---------------+----------------+----------------+

2. String evaluation (supports multiple formats)

SELECT is_true('t'), is_true('f');
+--------------+--------------+
| is_true('t') | is_true('f') |
+--------------+--------------+
| true         | false        |
+--------------+--------------+

3. Using in a WHERE clause

SELECT * FROM VALUES (true), (false), (NULL) AS t(flag)
WHERE is_true(flag);
+------+
| flag |
+------+
| true |
+------+