Question

我想在插入值时忽略或更新重复项。我知道on duplicate key，但我无法找到解决方案。这是示例表示例。

| ID   | roll     | sub   | mark |
| ---- |----------| ------|------|
|   1  | 100      | 11    |  15  |
|   2  | 101      | 11    |  16  |
|   3  | 102      | 11    |  17  |
|   4  | 100      | 12    |  10  |
|   5  | 101      | 12    |  11  |
|   6  | 102      | 12    |  12  |

此处id为primary key，但我想插入以检查roll & sub是否已存在，然后更新，否则插入新行。我尝试使用以下代码，但是插入了重复的行，但它应该更新下表中的第6行。

CREATE INDEX mycompo_index on student(roll,sub);

insert into student(roll, mark, sub)
            values (102, 22, 12)
on duplicate key update mark = values(mark);

Answer 1

如果sub和ALTER TABLE student ADD CONSTRAINT student_uq UNIQUE(roll, sub)的组合应该是唯一的，您应该在表格中定义这样一个键：

on duplicate key

请注意，如果您这样做，则不必显式创建您正在创建的索引，该约束将为您创建。一旦有了这个地方，您可以使用您尝试使用的INSERT INTO student(roll, mark, sub) VALUES (102, 22, 12) ON DUPLICATE KEY UPDATE mark = VALUES(mark)语法：

#Script to solve F issue
#----------------------------------------
#By Kapil Shirsath
#----------------------------------------

cd /var/spool/mail        #mail files reside in mail folder

filename=`ls -l | grep '^-' | sort -k 5 -rn | head -1 | tr -s " " "," | cut -d "," -f "9"`    # this will list the file with maximum size`

echo "File with maximum size is  $filename"
echo "----------------------------------------------------"
echo "Is it the file expected?(y/n)"
read choice
if test $choice == "n"
then
    echo "Exiting...."
    exit;
fi;

c=1
while [ $c -le 5 ]
do
    ls -l $filename
    echo $filename
    sleep 2
    c=`expr $c + 1`
done
echo "---------------------------------------------------"

#`sudo su`   #this will give you super user permissions
echo "First line of the file is as below :"
head -1 $filename
echo "---------------------------------------"
firstline=`head -1 $filename`;
echo "Repeat : $firstline"
echo $firstline | grep ^"rom" >/dev/null
if test $? -eq 0
then
    ex -s $filename <<'EOF'
    1s/^/F/
    :wq
    EOF
    echo "F issue fixed!"
    c=1
    while [ $c -le 5 ]
    do
        ls -l $filename
        sleep 2
        c=`expr $c + 1`
    done
    echo "---------------------------------------------------"  
else
    echo "Not finding the missing 'F' ! !! Kindly check with your system "
    exit;
fi;

插入如果在表中没有找到重复，则更新

1 个答案: