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SET @start_global_value = @@global.join_cache_level;
show global variables like 'join_cache_level';
Variable_name Value
join_cache_level #
show session variables like 'join_cache_level';
Variable_name Value
join_cache_level #
select * from information_schema.global_variables where variable_name='join_cache_level';
VARIABLE_NAME VARIABLE_VALUE
JOIN_CACHE_LEVEL #
select * from information_schema.session_variables where variable_name='join_cache_level';
VARIABLE_NAME VARIABLE_VALUE
JOIN_CACHE_LEVEL #
set global join_cache_level=4;
select @@global.join_cache_level;
@@global.join_cache_level
4
set session join_cache_level=4;
select @@session.join_cache_level;
@@session.join_cache_level
4
set global join_cache_level=1.1;
ERROR 42000: Incorrect argument type to variable 'join_cache_level'
set session join_cache_level=1e1;
ERROR 42000: Incorrect argument type to variable 'join_cache_level'
set global join_cache_level="foo";
ERROR 42000: Incorrect argument type to variable 'join_cache_level'
set global join_cache_level=0;
select @@global.join_cache_level;
@@global.join_cache_level
0
set session join_cache_level=cast(-1 as unsigned int);
Warnings:
Note 1105 Cast to unsigned converted negative integer to it's positive complement
Warning 1292 Truncated incorrect join_cache_level value: '18446744073709551615'
select @@session.join_cache_level;
@@session.join_cache_level
8
SET @@global.join_cache_level = @start_global_value;
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