I have two tables with identical structures. Let's call them table A and B.
Table A consists of records with ID as primary key from 1-10 and B has the table with IDs 11-20.
Given I have imported table A into mysql table, how can I, in a way, concatenate table B to A?
Any thoughts will be much appreciated :D
You use insert:
insert into tablea
select *
from tableb;
It is better to list the columns for the insert and select, but you can do it with this syntax if the tables really do have identical formats.
Related
I am new using mySQL, so probably my question will be very banal, but I didn't find any solution on internet.
I have two tables, TABLE 1 and TABLE 2, each one with a single primary key tab1PK (INT) and tab2PK (VARCHAR).
Since TABLE 1 and TABLE 2 have a M:N relationship, I have a third table, TABLE 3, whose PK are two: tab1PK and tab2PK.
I generated random data for TABLE 1 and TABLE 1. Is there a way to generate rapidly data for the TABLE 3? Is there a way to easily combine tab1PK and tab2PK?
This will give you a cartesian join of all table1 & table2 primary keys.
insert into table3 (tab1PK, tab2PK)
select table1.tab1PK, table2.tab2PK
from table1, table2
I'm working with phpmyadmin and I have to merge two db with same structure but different data.
The db have relation between tables (foreign key).
The data in two db may have same id, and so their foreign key.
I would like to know if it's possible merge the two db keeping all data, so, if a row already "exist", insert it with new id and update its foreign key.
thanks a lot
No easy way unfortunately. If you have TableA as a foreign key to TableB, you will need to
1) Insert data from source tableA to target tableA
2) create a (temp) table to store the mapping between source tableA ids and target tableA ids
3) Use this mapping table when inserting data from tableB to convert the tableA ids to the new ones in the target db
... and so on. It can get quite hairy if you have a deep hierarchy of tables, but hopefully you get the idea. Take backups before you start.
Another idea that you might want to consider is using a cursor:
Assume table A is the one that you want to keep and table B is the one you want to remove.
Declare a cursor for table B and select all the records.
Loop each record selected from the cursor and check.
Case 1: If the ID is exists on table A, insert the record to table A with same details.
Case 2: If the ID is exists on table B, insert the record and modify the ID and foreign key.
Once all the records have been checked, drop table B.
Sorry, I just can give an idea at the moment.
I have a table A, it has millions of records and it's growing. A new column needs be added to table A with indexing, but it could be headache to migrate such a large table. So table B is created at some point from table A, question is how to sync up these 2 tables efficiently?
There're multiple scenarios new records will be added to table A.
To 'Sync' up two tables without actually merging them you can create a UNION VIEW. A VIEW can be used just like a table for calculation, manipulation, data storage etc. This is assuming that both tables have the same amount of rows, if not you'll need to create primary and foreign keys.
CREATE OR REPLACE VIEW viewname AS
SELECT * FROM TABLE_A
UNION ALL
SELECT * FROM TABLE_B
Now if both tables don't share the same amount of rows you'll need at least 1 field in common between the two tables called primary and foreign keys, to join the tables using the primary and foreign keys you'll need to use a JOIN like this:
CREATE OR REPLACE VIEW viewname AS
SELECT TableA.FieldName, TableB.FieldName, TableA.FieldName
FROM TableA
LEFT JOIN TableB
ON TableA.primarykeyField = TableB.foreignkeyField
UNION ALL
SELECT TableA.FieldName, TableB.FieldName, TableA.FieldName
FROM TableA
RIGHT JOIN TableB
ON TableA.primarykeyField = TableB.foreignkeyField
It depends on what type of join you want but I think FULL JOIN will give you the best results, FULL JOIN's aren't supported in MySQL but using LEFT JOIN RIGHT JOIN and UNION ALL mimics the same results.
Or if you simply want to copy all the records from table A to table B you could use this.
INSERT INTO TableB
SELECT * FROM TableA;
Part 1:
In MySQL suppose I have Table A which has more columns than Table B. I want to transfer values from Table B to Table A where the id row in A matches the id Row in B and update the values in table A from the values in table B.
Part 2:
Table B is a superset of table A, so how does one insert ids and their corresponding values from table B into table A while also updating id's that are in table A.
Like FreshPrinceOfSO already mentioned in the comments, you won't get code for free here.
But here are at least the steps. Two possibilities. Either you split the work up in two statements, one update then one insert statement. Or you could work with
INSERT ... ON DUPLICATE KEY UPDATE ...
You would have to have an unique index on the table for this to work.
For the first solution mentioned you'd inner join the tables for the update first, that's trivial. Then for the insert you'd use a select with a left join and with is null checking for entries that are not already in the table.
Good luck...
Apologies if I am mistaken, but is there any way to create a table inside a column in MySql?
Brief: I have a table named test_table which contains a column named name test_column. Now I want to create a table inside test_column. Is this possible?
You would create a "child" table with an id that is referenced in the column of the main table. You wouldn't create a "table" in a column.
For example
Table 1
columm_pk int
column_fk int
table 2
column_pk (this is what goes in table 1)
other columns as needed.
then you just join the tables based on that fk id. You can have multiple fk column in the first table that link to different child tables. You can also look in to SET data types in MySql although I wouldn't recommend them.
btw, If your question is MySql specific then you shouldn't use the oracle tags.
No nested tables in MySql, but there is a SET datatype that you can use in a table
http://dev.mysql.com/doc/refman/5.0/en/set.html
That approach is not possible. What you are looking for is a second table that is linked using a field in the first table.
Example:
test_table:
ID | column1 | some more columns
test_table2:
table1_ID | column1| column2...
You can then access them using JOIN commands. For example:
SELECT *
FROM test_table t1
INNER JOIN test_table2 t2
ON t1.ID = t2.table1_ID
This way you can have multiple rows for each ID in table 1, which has the effect you are looking for.
This is not possible in MySQL.