Question

I was browsing on MySQL Documentation about the update. See UPDATE Syntax. I found out that the syntax is

UPDATE [LOW_PRIORITY] [IGNORE] table_reference
    SET col_name1={expr1|DEFAULT} [, col_name2={expr2|DEFAULT}] ...
    [WHERE where_condition]
    [ORDER BY ...]
    [LIMIT row_count]

When I executed this statement

UPDATE SampleTB
SET NAME = '123' AND Address = '456'
WHERE ID = 1;

See Here for SQL Fiddle Demonstration Link

The query executed successfully and the value of Name was 0. I was expecting a syntax error on the query.

Can somebody explain to me why it didn’t generate an error? And why was the new value of the column is zero and not 123?

Answer 1

SET NAME = '123' AND Address = '456'

is parsed to something like:

SET NAME = ('123' AND (Address = '456'))

which is one comparison and boolean AND of a string and boolean operands.

So it takes the current row’s Address column value, compares it to a '456' string and result of the comparison is used as a second operand for AND like '123' AND false