在一个会话中创建的预处理语句对于其他会话不可用。A prepared statement created in one session is not available to other sessions.

当会话结束时，无论是正常还是异常，其预处理语句均不再存在。如果启用自动重连，客户端不会收到连接丢失的通知。因此，客户端可能希望禁用自动重连。参见自动重连控制。When a session ends, whether normally or abnormally, its prepared statements no longer exist. If auto-reconnect is enabled, the client is not notified that the connection was lost. For this reason, clients may wish to disable auto-reconnect. See Automatic Reconnection Control.

在存储程序中创建的预处理语句在程序执行完成后仍然存在，并可以在程序外部执行。A prepared statement created within a stored program continues to exist after the program finishes executing and can be executed outside the program later.

在存储程序上下文中编写的语句不能引用存储过程或函数参数或本地变量，因为程序结束时这些参数会超出作用域，且如果该语句在程序外执行时将无法使用。作为一种变通方法，可以参考用户自定义变量，它们也有会话作用域;参见 第 11.4 节，“用户定义变量”。A statement prepared in stored program context cannot refer to stored procedure or function parameters or local variables because they go out of scope when the program ends and would be unavailable were the statement to be executed later outside the program. As a workaround, refer instead to user-defined variables, which also have session scope; see Section 11.4, “User-Defined Variables”.

作为二元算术算子操作数的参数与另一个操作数具有相同的数据类型。A parameter which is an operand of a binary arithmetic operator has the same data type as the other operand.

如果一个二元算术算子的两个操作数都是参数，则参数的类型由该运算符的上下文决定。If both operands of a binary arithmetic operator are parameters, the type of the parameters is decided by the context of the operator.

如果参数是一元算术算子的操作数，则参数的类型由该运算符的上下文决定。If a parameter is the operand of a unary arithmetic operator, the parameter's type is decided by the context of the operator.

如果算术算子没有类型决定上下文，任何相关参数的派生类型为DOUBLE PRECISION例如，当参数是SELECT list“，或者它是比较运算符的一部分时，就会发生这种情况。If an arithmetic operator has no type-determining context, the derived type for any parameters involved is DOUBLE PRECISION. This can happen, for example, when the parameter is a top-level node in a SELECT list, or when it is part of a comparison operator.

作为字符字符串操作符的参数与其他操作数的聚合类型具有相同的派生类型。如果运算符的所有操作数都是参数，派生类型为VARCHAR其排序由 collation_connection。A parameter which is an operand of a character string operator has the same derived type as the aggregated type of the other operands. If all operands of the operator are parameters, the derived type is VARCHAR; its collation is determined by the value of collation_connection.

参数作为时间运算符的操作数类型为 DATETIME 如果操作符返回 DATETIMETIME 如果运算符返回 TIME且DATE，如果操作员返回 DATEA parameter which is an operand of a temporal operator has type DATETIME if the operator returns a DATETIME, TIME if the operator returns a TIME, and DATE if the operator returns a DATE.

作为二元比较算子操作数的参数与比较操作子的另一个操作数具有相同的派生类型。A parameter which is an operand of a binary comparison operator has the same derived type as the other operand of the comparison.

作为三元比较算子操作数的参数，如BETWEEN）具有与其他操作数聚合类型相同的派生类型。A parameter that is an operand of a ternary comparison operator such as BETWEEN has the same derived type as the aggregated type of the other operands.

如果比较算子的所有操作数都是参数，每个操作数的派生类型为VARCHAR其排序由 collation_connection。If all operands of a comparison operator are parameters, the derived type for each of them is VARCHAR, with collation determined by the value of collation_connection.

参数是任意一个输出操作数的参数 CASE， COALESCE， IF IFNULL，或 NULLIF 的派生类型与运算符其他输出操作数的聚合类型相同。A parameter that is an output operand of any of CASE, COALESCE, IF, IFNULL, or NULLIF has the same derived type as the aggregated type of the operator's other output operands.

如果 CASECOALESCE， IF IFNULL或者 NULLIF是参数，或者它们都是 NULL参数的类型由操作符的上下文决定。If all output operands of any of CASE, COALESCE, IF, IFNULL, or NULLIF are parameters, or they are all NULL, the type of the parameter is decided by the context of the operator.

如果参数是CASE的操作数，COALESCE() IF或 IFNULL，且没有类型决定上下文，每个参数的派生类型为VARCHAR），其对照由 collation_connection。If the parameter is an operand of any of CASE, COALESCE(), IF, or IFNULL, and has no type-determining context, the derived type for each of the parameters involved is VARCHAR, and its collation is determined by the value of collation_connection.

参数是 CAST() 的操作数，其类型与 CAST()A parameter which is the operand of a CAST() has the same type as specified by the CAST().

如果参数是 SELECT 列表，且不属于 INSERT 语句，该参数的派生类型为 VARCHAR其排序值由 collation_connection。If a parameter is an immediate member of a SELECT list that is not part of an INSERT statement, the derived type of the parameter is VARCHAR, and its collation is determined by the value of collation_connection.

如果参数是 SELECT，该列表属于 INSERT 语句，那么该参数的派生类型就是插入该参数的对应列的类型。If a parameter is an immediate member of a SELECT list that is part of an INSERT statement, the derived type of the parameter is the type of the corresponding column into which the parameter is inserted.

如果一个参数被用作 UPDATE 语句的 SET 子句或 INSERT 语句的 ON DUPLICATE KEY UPDATE 子句中的赋值源，则该参数的派生类型为由 SET 或 ON DUPLICATE KEY UPDATE 子句更新的相应列的类型。If a parameter is used as source for an assignment in a SET clause of an UPDATE statement or in the ON DUPLICATE KEY UPDATE clause of an INSERT statement, the derived type of the parameter is the type of the corresponding column which is updated by the SET or ON DUPLICATE KEY UPDATE clause.

如果参数是函数的参数，则派生类型取决于函数的返回类型。If a parameter is an argument of a function, the derived type depends on the function's return type.

使用 NULL 作为实际参数值。NULL is used as the actual parameter value.

参数是 CAST() 的操作数。（在这种情况下，会尝试将其转换为派生类型，如果转换失败则抛出异常。）A parameter is an operand of a CAST(). (Instead, a cast to the derived type is attempted, and an exception raised if the cast fails.)

参数是字符串。（在这种情况下，会执行隐式 CAST(? AS derived_type)。）A parameter is a string. (In this case, an implicit CAST(? AS derived_type) is performed.)

参数的派生类型和实际类型都是 INTEGER 且符号相同。The derived type and actual type of the parameter are both INTEGER and have the same sign.

参数的派生类型是 DECIMAL，实际类型为 DECIMAL 或 INTEGER。The parameter's derived type is DECIMAL and its actual type is either DECIMAL or INTEGER.

派生类型是 DOUBLE，实际类型是任何数值类型。The derived type is DOUBLE and the actual type is any numeric type.

派生类型和实际类型都是字符串类型。Both the derived type and the actual type are string types.

如果派生类型是时间类型且实际类型也是时间类型。例外：派生类型是 TIME 而实际类型不是 TIME；派生类型是 DATE 而实际类型不是 DATE。If the derived type is temporal and the actual type is temporal. Exceptions: The derived type is TIME and the actual type is not TIME; the derived type is DATE and the actual type is not DATE.

派生类型是时间类型而实际类型是数值类型。The derived type is temporal and the actual type is numeric.