问单次mysql查询:使表和数据库中有列的值为空

EN

UPDATE table1 , table2 SET table1.column = 0 , table2.column =0

SELECT CONCAT("UPDATE `", TABLE_SCHEMA,"`.`", TABLE_NAME, "` SET `",COLUMN_NAME,"` = 0 ") AS MySQLCMD FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = "you_db_name_here"

SET @query :="";
SELECT @query := CONCAT("UPDATE `", TABLE_SCHEMA,"`.`", TABLE_NAME, "` SET `",COLUMN_NAME,"` = 0 ") AS MySQLCMD FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = "you_db_name_here";
PREPARE stmt FROM @query;
EXECUTE stmt;

SET @query :="";
SELECT @query := CONCAT("UPDATE `", C.TABLE_SCHEMA,"`.`", C.TABLE_NAME, "` SET `",C.COLUMN_NAME,"` = '' ") AS MySQLCMD from information_Schema.Columns C LEFT JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE U ON C.COLUMN_NAME = U.COLUMN_NAME WHERE C.TABLE_SCHEMA = "you_db_name_here" AND U.CONSTRAINT_NAME is NULL;
PREPARE stmt FROM @query;
EXECUTE stmt;

truncate table t;

update t
    set col1 = null,
        col2 = null,
        . . .;

$sql="SELECT CONCAT('UPDATE ', TABLE_SCHEMA,'.', TABLE_NAME, ' SET ',COLUMN_NAME,' = 0;') AS MySQLCMD FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'DATABASE_NAME' ";

$result=$conn->query($sql);
if($result->num_rows> 0){
while($row=$result->fetch_assoc()){
    $exe=$conn->query($row['MySQLCMD']);
}