MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
The Performance Schema provides a
user_variables_by_thread table that
exposes user-defined variables. These are variables defined
within a specific session and include a @
character preceding the name; see
Section 9.4, “User-Defined Variables”.
The user_variables_by_thread table
has these columns:
THREAD_ID
The thread identifier of the session in which the variable is defined.
VARIABLE_NAME
The variable name, without the leading @
character.
VARIABLE_VALUE
The variable value.
TRUNCATE TABLE is not permitted
for the user_variables_by_thread
table.