[英]mysql insert if value not exist in another table
I have two tables that store value as VARCHAR
.我有两个表将值存储为
VARCHAR
。
I'm populating table and I want just insert values in one of tables if they are not exist in other table.我正在填充表,如果其他表中不存在值,我只想在其中一个表中插入值。
Something like:就像是:
INSERT IF IS EMPTY(SELECT * FROM t1 where v='test') INTO t2 (v) VALUES ('test')
How Can I do that?我怎样才能做到这一点?
You need to use some type ofINSERT...SELECT
query.您需要使用某种类型的
INSERT...SELECT
查询。
Update (after clarification): For example, here is how to insert a row in t2
if a corresponding row do not already exist in t1
:更新(澄清后):例如,如果相应的行在
t1
不存在,这里是如何在t2
插入一行:
INSERT INTO t2 (v)
SELECT temp.candidate
FROM (SELECT 'test' AS candidate) temp
LEFT JOIN t1 ON t1.v = temp.candidate
WHERE t1.v IS NULL
To insert multiple rows with the same query, I 'm afraid there is nothing better than用相同的查询插入多行,恐怕没有什么比
INSERT INTO t2 (v)
SELECT temp.candidate
FROM (
SELECT 'test1' AS candidate
UNION SELECT 'test2'
UNION SELECT 'test3' -- etc
) temp
LEFT JOIN t1 ON t1.v = temp.candidate
WHERE t1.v IS NULL
Original answer原答案
For example, this will take other_column
from all rows from table1
that satisfy the WHERE
clause and insert rows into table2
with the values used as column_name
.例如,这将从
table1
中满足WHERE
子句的所有行中获取other_column
并将行插入table2
,其值用作column_name
。 It will ignore duplicate key errors.它将忽略重复的键错误。
INSERT IGNORE INTO table2 (column_name)
SELECT table1.other_column
FROM table1 WHERE table1.something == 'filter';
for insertion of Multiple columns you can try this.对于插入多列,你可以试试这个。
INSERT INTO table_1 (column_id,column_2,column_3,column_4,column_5)
SELECT
table_2.*
FROM
table_2
LEFT JOIN table_1 ON table_1.column_id = table_2.column_id
WHERE
table_1.column_id IS NULL;
INSERT IGNORE INTO table_1(col1,col2,col3,col4)
SELECT table_2.*
FROM table_2;
The above statement does the perfect job in your scenario.上面的语句在您的场景中做得很完美。
Kinda ghetto.. but works.有点贫民窟..但有效。 Assumes that you are inserting a static value into 'col'
假设您将静态值插入到“col”中
INSERT INTO t1 (col)
SELECT 'test'
FROM t2
WHERE (SELECT count(*) FROM t2 WHERE v='test') = 0;
$result = mysql_query("SELECT * FROM t1 WHERE v='test'");
if(mysql_num_rows($result) == 0){
mysql_query("INSERT INTO t2 (v) VALUES ('test')");
}
Haven't been using mysql for a while so these functions are deprecated, but this is how I should do it.有一段时间没有使用 mysql,所以这些功能已被弃用,但我应该这样做。
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