I came accross the sql query where the <=>
operator is put. What does <=> operator mean?
SELECT STR_ID, TEX_TEXT AS STR_DES_TEXT, IF( EXISTS( SELECT * FROM SEARCH_TREE AS SEARCH_TREE2 WHERE SEARCH_TREE2.STR_ID_PARENT <=> SEARCH_TREE.STR_ID LIMIT 1 ), 1, 0) AS DESCENDANTS FROM SEARCH_TREE
This sql is of MySQL type.
When in doubt, read the documentation :
<=> is a NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL.
Null safe equal operator,it returns 1 if boths operands are null.
http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#operator_equal-to
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