I have two tables. In table one (table_1) I have id, category_name and category_id. Here only id is set. In another one (table_2) I have article_id, content_id and tag_name.
Now from table_1 and table_2 I need to put content_id and tag_name from second into first table category_id and category_name. This can be done like this:
UPDATE table_1
INNER JOIN table_2 ON table_2.article_id = table_1.id
SET table_1.category_id = table_2.content_id
UPDATE table_1
INNER JOIN table_2 ON table_2.article_id = table_1.id
SET table_1.category_name = table_2.tag_name
I tried adding AND and add table_1.category_name = table_2.tag_name, but I didn't get anything so I split the two queries.
But the issue I have is that in my second table, I can have multiple content_id's attached to the same article_id (multiple categories in same article), and with the above I'll only get one integer put in the category_id for an article in the first table.
table_2 for instance:
article_id content_id tag_name
================================
21596 156 Tag Name
21596 16 Second
26189 156 Tag Name
How can I update values from one table to another if there is no one-to-one correspondence? Also, can these values be comma separated?
CLARIFICATION
What I need is a way to pull both tag_names and content_ids from the second table to first table and have something like
table_1:
id category_id category_name
=========================================
21596 156, 16 Tag Name, Second
26189 156 Tag Name
UPDATE
Ok, so I found a way to get all the info concatenated into one from second table, I just need to incorporate this somehow into my update query
SELECT article_id, group_concat(tag_name ORDER BY tag_name, content_id) AS tag_name, group_concat(content_id ORDER BY tag_name, content_id) AS tag_id
FROM table_2
GROUP BY article_id
this will work
UPDATE table_1
INNER JOIN table_2 ON table_2.article_id = table_1.id
SET table_1.category_id = table_2.content_id, table_1.category_name = table_2.tag_name
UPDATE
In oracle , we can achieve with the below LISTAGG function which basically concats columns based on group. Mysql does have a counterpart take a look at this Thread
create table temp
(
article number(2),
test varchar2(30)
)
insert into temp values(1, null);
create table temp_table
(
article number(2),
test varchar2(10)
)
insert into temp_table values(1, 'System');
insert into temp_table values(1, 'Source');
update temp t
set t.test = (
select LISTAGG(test) WITHIN GROUP (order by test) from temp_table tt
where tt.article = t.article
group by
tt.article)
Ok, so the answer is doing two updates one for one column, and one for second column (maybe there's a way to merge those two, but so far this works)
UPDATE
table_1
JOIN (SELECT article_id, GROUP_CONCAT(tag_name ORDER BY tag_name, content_id) AS tag_name
FROM table_2
GROUP BY article_id) table_2
ON table_1.id = table_2.article_id
SET table_1.category_name = table_2.content_name
I am updating first table, but before that I'm concatenating the tag_name in second table, so that I get all tags for one article. Then I just set those values in first table.
The same for id works.
Related
I have three tables with contents, now i want to get them and add it into new table but am having this sql error "Column count doesn't match value count at row 1"
here is the sql query.
insert into compare_year(yeara,yearb,yearc,data)
SELECT yeara
FROM table_1
UNION ALL
SELECT yearb, data
FROM table_2
UNION ALL
SELECT yearc
FROM table_3
below is how i created the tables
create table table_1(id int primary key auto_increment,yeara varchar(100));
create table table_2(id int primary key auto_increment,yearb varchar(100),data varchar(100));
create table table_3(id int primary key auto_increment,yearc varchar(100));
my new table is now
create table compare_year(id int primary key auto_increment,yeara varchar(100),yearb varchar(100),yearc varchar(100),data varchar(100))
please can someone help me. thanks
Note:when you union select queries,the number of columns should be equal.
and also you cannot insert mutiple select columns into a single row of another.
My solution will be like:
if three table contain same id,then you can do like this
insert into compare_year(yeara,yearb,yearc,data)
SELECT T1.yeara,T2.yearb,T3.yearc,T2.data
FROM table_1 T1
left Join table_2 T2 on T2.Id = T1.Id
left Join table_3 T3 on T3.Id = T2.Id
It looks like what you want is a JOIN rather than a UNION. When you union two select statements, they must have the same number of fields in the SELECT. For example,
insert into compare_year(yeara)
SELECT yeara
FROM table_1
UNION ALL
SELECT yearb AS yeara
FROM table_2
UNION ALL
SELECT yearc AS yeara
FROM table_3
would be acceptable syntactically. If you want to join the tables,
INSERT INTO compare_year(yeara, yearb, yearc, data)
SELECT table_1.yeara, table_2.yearb, table_3.yearc, table_2.data
FROM table_1, table_2, table_3
but note that this is full cartesian product of the tables. It's likely you want some conditionals as well in a WHERE clause. It's also worth noting that the order of the select cause is what's important for the INSERT, not the field names.
We have 2 tables called : "post" and " post_extra"
summery construction of "post" table's are: id,postdate,title,description
And for post_extra they are: eid,news_id,rating,views
"id" filed in the first table is related to "news_id" to the second table.
There are more than 100,000 records on the table, that many of them are duplicated. I want to keep only one record and remove duplicate records on "post" table that have the same title, and then remove the related record on "post_extra"
I ran this query on phpmyadmin but the server was crashed. And I had to restart it.
DELETE e
FROM Post p1, Post p2, Post_extra e
WHERE p1.postdate > p2.postdate
AND p1.title = p2.title
AND e.news_id = p1.id
How can I do this?
Suppose you have table named as 'tables' in which you have the duplicate records.
Firstly you have to do group by column on which you want to delete duplicate.But I am not doing it with group by.I am writing self join instead of writing nested query or creating temporary table.
SELECT * FROM `names` GROUP BY title, id having count(title) > 1;
This query return number of duplicate records with their title and id.
You don't need to create the temporary table in this case.
To Delete duplicate except one record:
In this table it should have auto increment column. The possible solution that I've just come across:
DELETE t1 FROM tables t1, tables t2 WHERE t1.id > t2.id AND t1.title = t2.title
if you want to keep the row with the lowest auto increment id value OR
DELETE t1 FROM tables t1, tables t2 WHERE t1.id < t2.id AND t1.title = n2.title
if you want to keep the row with the highest auto increment id value.
You can cross check your solution,by selecting the duplicate records again by given query:
SELECT * FROM `tables` GROUP BY title, id having count(title) > 1;
If it return 0 result, then you query is successful.
This will keep entries with the lowest id for each title
DELETE p, e
FROM Post p
left join Post_extra e on e.news_id = p.id
where id not in
(
select * from
(
select min(id)
from post
group by title
) x
)
SQLFiddle demo
You can delete duplicate record by creating a temporary table with unique index on the fields that you need to check for the duplicate value
then issue
Insert IGNORE into select * from TableWithDuplicates
You will get a temporary table without duplicates .
then delete the records from the original table (TableWithDuplicates) by JOIN the tables
Should be something like
CREATE TEMPORARY TABLE `tmp_post` (
`id` INT(10) NULL,
`postDate` DATE NULL,
`title` VARCHAR(50) NULL,
`description` VARCHAR(50) NULL, UNIQUE INDEX `postDate_title_description` (`postDate`, `title`, `description`) );
INSERT IGNORE INTO tmp_post
SELECT id,postDate,title,description
FROM post ;
DELETE post.*
FROM post
LEFT JOIN tmp_post tmp ON tmp.id = post.id
WHERE tmp.id IS NULL ;
Sorry I didn't tested this code
I have two tables Board1 and Board2 with the identical structure. They both have a primary index column of id. I have a THIRD table called Table1, which has a non-indexed column board_id, where the same board_id occurs multiple times. board_id always corresponds to an id in Board1. Board2 is currently empty, and I want to add rows from Board1, but only where the same board_id occurs at least six times in Table1. Table1 will be changing periodically, so I'll be needing to do the query in the future, but without doubling id rows which are already in Board2.
So to recap:
There are three tables: Board1, Board2, and Table1. I want to copy rows from Board1 to Board2, but only where the id in the Board1 occurs (at least) six times in Table1 as `board_id'.
I'd appreciate any help!
EDIT: I'm dreadfully sorry, but I realized I made a huge mistake in my question. I've rewritten it to reflect what I actually needed. I'm truly sorry.
You can do it like this
INSERT INTO Table2
SELECT
id,
board_id
FROM (SELECT
b.id,
b.board_id,
bl.Count
FROM board as b
LEFT JOIN (SELECT
board_id,
COUNT(board_id) as `Count`
FROM board
GROUP BY board_id) as bl
on bl.board_id = b.board_id
group by b.id
having bl.Count >= 6) as L
If you need more columns you can select them in inner and outer queries.
Fiddle Demo for Select
Here is what you asked for, with fiddle
INSERT Table2
SELECT
*
FROM
Table1
JOIN
(
SELECT
Board_Id,
count(*) cnt
FROM
Table1
GROUP BY
Board_Id
) BoardIds
ON BoardIds.Board_Id = Table1.Board_Id
WHERE
BoardIds.cnt > 5
AND
NOT EXISTS (SELECT id FROM Table2 WHERE Table2.id = Table1.id)
Try something like the below:
Add your column names where specified (excluding any ID columns), as I'm assuming each row will have a unique ID, so you won't be able to GROUP and COUNT by doing SELECT * FROM Table1
You may need to test / validate this
INSERT INTO Board2 (Your Column Names)
SELECT (Your Column Names)
FROM Board1
WHERE id (IN (SELECT board_id
FROM Table1
GROUP BY (board_id)
HAVING (COUNT(*) >= 6))
AND board_id NOT IN(SELECT DISTINCT board_id FROM Board2)
Say I have table1 which contains a field called Name and a field called ItemID which is a foreign key to table2.
What I want is a query that contains each Name, and how many entries in table2 have the same ItemID as that entry.
How would I go about doing this?
select Name, count(ItemID) as itemCount
from table1 inner join table2 on table1.ItemID = table2.id
group by Name
but my sql-fu may be rusty :P
Note that this will give no rows for Names where table2 contains no matching rows, so itemCould will always be >0
I have a table with some ids + titles. I want to make the title column unique, but it has over 600k records already, some of which are duplicates (sometimes several dozen times over).
How do I remove all duplicates, except one, so I can add a UNIQUE key to the title column after?
This command adds a unique key, and drops all rows that generate errors (due to the unique key). This removes duplicates.
ALTER IGNORE TABLE table ADD UNIQUE KEY idx1(title);
Edit: Note that this command may not work for InnoDB tables for some versions of MySQL. See this post for a workaround. (Thanks to "an anonymous user" for this information.)
Create a new table with just the distinct rows of the original table. There may be other ways but I find this the cleanest.
CREATE TABLE tmp_table AS SELECT DISTINCT [....] FROM main_table
More specifically:
The faster way is to insert distinct rows into a temporary table. Using delete, it took me a few hours to remove duplicates from a table of 8 million rows. Using insert and distinct, it took just 13 minutes.
CREATE TABLE tempTableName LIKE tableName;
CREATE INDEX ix_all_id ON tableName(cellId,attributeId,entityRowId,value);
INSERT INTO tempTableName(cellId,attributeId,entityRowId,value) SELECT DISTINCT cellId,attributeId,entityRowId,value FROM tableName;
DROP TABLE tableName;
INSERT tableName SELECT * FROM tempTableName;
DROP TABLE tempTableName;
Since the MySql ALTER IGNORE TABLE has been deprecated, you need to actually delete the duplicate date before adding an index.
First write a query that finds all the duplicates. Here I'm assuming that email is the field that contains duplicates.
SELECT
s1.email
s1.id,
s1.created
s2.id,
s2.created
FROM
student AS s1
INNER JOIN
student AS s2
WHERE
/* Emails are the same */
s1.email = s2.email AND
/* DON'T select both accounts,
only select the one created later.
The serial id could also be used here */
s2.created > s1.created
;
Next select only the unique duplicate ids:
SELECT
DISTINCT s2.id
FROM
student AS s1
INNER JOIN
student AS s2
WHERE
s1.email = s2.email AND
s2.created > s1.created
;
Once you are sure that only contains the duplicate ids you want to delete, run the delete. You have to add (SELECT * FROM tblname) so that MySql doesn't complain.
DELETE FROM
student
WHERE
id
IN (
SELECT
DISTINCT s2.id
FROM
(SELECT * FROM student) AS s1
INNER JOIN
(SELECT * FROM student) AS s2
WHERE
s1.email = s2.email AND
s2.created > s1.created
);
Then create the unique index:
ALTER TABLE
student
ADD UNIQUE INDEX
idx_student_unique_email(email)
;
Below query can be used to delete all the duplicate except the one row with lowest "id" field value
DELETE t1 FROM table_name t1, table_name t2 WHERE t1.id > t2.id AND t1.name = t2.name
In the similar way, we can keep the row with the highest value in 'id' as follows
DELETE t1 FROM table_name t1, table_name t2 WHERE t1.id < t2.id AND t1.name = t2.name
This shows how to do it in SQL2000. I'm not completely familiar with MySQL syntax but I'm sure there's something comparable
create table #titles (iid int identity (1, 1), title varchar(200))
-- Repeat this step many times to create duplicates
insert into #titles(title) values ('bob')
insert into #titles(title) values ('bob1')
insert into #titles(title) values ('bob2')
insert into #titles(title) values ('bob3')
insert into #titles(title) values ('bob4')
DELETE T FROM
#titles T left join
(
select title, min(iid) as minid from #titles group by title
) D on T.title = D.title and T.iid = D.minid
WHERE D.minid is null
Select * FROM #titles
delete from student where id in (
SELECT distinct(s1.`student_id`) from student as s1 inner join student as s2
where s1.`sex` = s2.`sex` and
s1.`student_id` > s2.`student_id` and
s1.`sex` = 'M'
ORDER BY `s1`.`student_id` ASC
)
The solution posted by Nitin seems to be the most elegant / logical one.
However it has one issue:
ERROR 1093 (HY000): You can't specify target table 'student' for
update in FROM clause
This can however be resolved by using (SELECT * FROM student) instead of student:
DELETE FROM student WHERE id IN (
SELECT distinct(s1.`student_id`) FROM (SELECT * FROM student) AS s1 INNER JOIN (SELECT * FROM student) AS s2
WHERE s1.`sex` = s2.`sex` AND
s1.`student_id` > s2.`student_id` AND
s1.`sex` = 'M'
ORDER BY `s1`.`student_id` ASC
)
Give your +1's to Nitin for coming up with the original solution.
Deleting duplicates on MySQL tables is a common issue, that usually comes with specific needs. In case anyone is interested, here (Remove duplicate rows in MySQL) I explain how to use a temporary table to delete MySQL duplicates in a reliable and fast way (with examples for different use cases).
In this case, something like this should work:
-- create a new temporary table
CREATE TABLE tmp_table1 LIKE table1;
-- add a unique constraint
ALTER TABLE tmp_table1 ADD UNIQUE(id, title);
-- scan over the table to insert entries
INSERT IGNORE INTO tmp_table1 SELECT * FROM table1 ORDER BY sid;
-- rename tables
RENAME TABLE table1 TO backup_table1, tmp_table1 TO table1;