I have 2 tables and I can't merge the values of these tables into table2.
Table1:
id | studnum | fname | lname | mname
1 | 1001 | Mark | Lei | Ramos
Table2:
id | studnum | remarks
Is it possible that when I input the values into Table2, the studnum from Table1 will input into Table2 also?
I tried this but it doesn't worked.
$sql = "SELECT table1.studnum FROM table1, table2
WHERE table1.studnum = table2.studnum";
So that the Table2 will be like this output
id | studnum | remarks
1 | 1001 | good
What you're looking for is using a JOIN Statement.
If the shared key is between them is studnum, you can do
SELECT * FROM table1
JOIN table2
ON table1.studnum = table2.studnum
Try a MySQL join function. Example:
SELECT *
FROM table1
JOIN table2
ON table1.studnum=table2.studnum;
More reading on joins: http://www.keithjbrown.co.uk/vworks/mysql/mysql_p5.php
If those are exactly your tables you dont really need what you are requesting as it goes against normalization.
In the case you will only have one or none remarks for an entry in table 1 there is no need for table 2, the remarks should be in table 1.
In the case you need multiple remarks for a single entry in table 1, you dont need stdnum in table 2. If your problem in this scenario is to construct a query to get the remakrs based on stdnums you can easily achieve this with a joint.
The only field you should be duplicating from table to table for a record/object is the id. You can (and may be should) scrifice normalization in pro of efficiency but your example is not the case.
Related
Is it possible to join 2 tables together on the basis of table 1 column value equaling table_2 column name?
table_1 table_2
----- -------------
| A | | 1 | 2 | 3 |
|---| |-----------|
| 1 | | Q | W | E |
----- -------------
Desired result is:
Select A from table_1 join table_2 WHERE table_1 A = table_2 column name.
Result:
1Q
I am using PHP, sorry for the poor psudo SQL, I honestly have no idea how to word it. Thank you for any help you can offer!
You want SQL where you use a value from one column as the name of another column. You Can't Do That™. In pure SQL queries the names of tables and columns must be literals (using the lingo of php style languages.
You probably can get the result you need by reading your tables into RAM with your php program, then programming your table-to-table correlation.
SELECT CONCAT(table_1.A,"",table_2.1) as RESULT
FROM table_1
LEFT JOIN table_2 ON table_1.A = table_2.1
I've got the following two tables (in MySQL):
Phone_book
+----+------+--------------+
| id | name | phone_number |
+----+------+--------------+
| 1 | John | 111111111111 |
+----+------+--------------+
| 2 | Jane | 222222222222 |
+----+------+--------------+
Call
+----+------+--------------+
| id | date | phone_number |
+----+------+--------------+
| 1 | 0945 | 111111111111 |
+----+------+--------------+
| 2 | 0950 | 222222222222 |
+----+------+--------------+
| 3 | 1045 | 333333333333 |
+----+------+--------------+
How do I find out which calls were made by people whose phone_number is not in the Phone_book? The desired output would be:
Call
+----+------+--------------+
| id | date | phone_number |
+----+------+--------------+
| 3 | 1045 | 333333333333 |
+----+------+--------------+
There's several different ways of doing this, with varying efficiency, depending on how good your query optimiser is, and the relative size of your two tables:
This is the shortest statement, and may be quickest if your phone book is very short:
SELECT *
FROM Call
WHERE phone_number NOT IN (SELECT phone_number FROM Phone_book)
alternatively (thanks to Alterlife)
SELECT *
FROM Call
WHERE NOT EXISTS
(SELECT *
FROM Phone_book
WHERE Phone_book.phone_number = Call.phone_number)
or (thanks to WOPR)
SELECT *
FROM Call
LEFT OUTER JOIN Phone_Book
ON (Call.phone_number = Phone_book.phone_number)
WHERE Phone_book.phone_number IS NULL
(ignoring that, as others have said, it's normally best to select just the columns you want, not '*')
SELECT Call.ID, Call.date, Call.phone_number
FROM Call
LEFT OUTER JOIN Phone_Book
ON (Call.phone_number=Phone_book.phone_number)
WHERE Phone_book.phone_number IS NULL
Should remove the subquery, allowing the query optimiser to work its magic.
Also, avoid "SELECT *" because it can break your code if someone alters the underlying tables or views (and it's inefficient).
The code below would be a bit more efficient than the answers presented above when dealing with larger datasets.
SELECT *
FROM Call
WHERE NOT EXISTS (
SELECT 'x'
FROM Phone_book
WHERE Phone_book.phone_number = Call.phone_number
);
SELECT DISTINCT Call.id
FROM Call
LEFT OUTER JOIN Phone_book USING (id)
WHERE Phone_book.id IS NULL
This will return the extra id-s that are missing in your Phone_book table.
I think
SELECT CALL.* FROM CALL LEFT JOIN Phone_book ON
CALL.id = Phone_book.id WHERE Phone_book.name IS NULL
SELECT t1.ColumnID,
CASE
WHEN NOT EXISTS( SELECT t2.FieldText
FROM Table t2
WHERE t2.ColumnID = t1.ColumnID)
THEN t1.FieldText
ELSE t2.FieldText
END FieldText
FROM Table1 t1, Table2 t2
SELECT name, phone_number FROM Call a
WHERE a.phone_number NOT IN (SELECT b.phone_number FROM Phone_book b)
Alternatively,
select id from call
minus
select id from phone_number
Don't forget to check your indexes!
If your tables are quite large you'll need to make sure the phone book has an index on the phone_number field. With large tables the database will most likely choose to scan both tables.
SELECT *
FROM Call
WHERE NOT EXISTS
(SELECT *
FROM Phone_book
WHERE Phone_book.phone_number = Call.phone_number)
You should create indexes both Phone_Book and Call containing the phone_number. If performance is becoming an issue try an lean index like this, with only the phone number:
The fewer fields the better since it will have to load it entirely. You'll need an index for both tables.
ALTER TABLE [dbo].Phone_Book ADD CONSTRAINT [IX_Unique_PhoneNumber] UNIQUE NONCLUSTERED
(
Phone_Number
)
WITH (STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ONLINE = ON) ON [PRIMARY]
GO
If you look at the query plan it will look something like this and you can confirm your new index is actually being used. Note this is for SQL Server but should be similar for MySQL.
With the query I showed there's literally no other way for the database to produce a result other than scanning every record in both tables.
I want to save multiple rows with single id store in table. What should I do? Please guide me.
For example:
| table1 |
|-----------------|
|id |name |
|001(pk) |Ajit |
| table2 |
|-----------------|
|id(FK) |address |
|001 |Pune |
|001 |Mumbai. |
means TWO TABLES are their in table1 id is primary key & table2 id is foreign key
i.e.: 001 id should multiple address it would be save into table2 but id must be same,
i.e.: address textbox will generate at runtime
Put its(id) default value as "001"(you deserve it) using mysql query and then while inserting a new entry leave that column to add as new.
If you're wanting to link the data in the two tables (i.e. a users table and an addresses table) just use a foreign key.
Your users table:
id | name
================
1 | Martin Bean
Your addresses table:
id | user_id | address
==================================
1 1 Newcastle upon Tyne
This way, the primary key of your addresses table is not dependent on the ID of the users table. And your query to fetch both pieces of data is easy with a join:
SELECT
u.id,
u.name,
a.address
FROM
users u
LEFT JOIN
addresses a ON u.id = a.user_id
I have many a times tried using nested query for MySQL in PHP, but it does not work. Is it not possible to do nested/Joins queries?
Just a Scenario:
I have two tables one table with user id and the other with data. User logins and with sessions I have to cross check two different tables with user id (user and data). Is it not possible to nest/join these two tables to write a single query statement.
In short is nesting or joining two or more tables permitted in PHP coding?
YES, it is possible to join two or more tables in MySQL (and therefore, also when using PHP).
You need to post your table schema, if you want us to show a relevant join query. You could, however, try something like:
SELECT * FROM user AS t1
CROSS JOIN data AS t2
ON t1.userid=t2.userid
WHERE t1.userid='154'
(This query presumes that there always will be one row with the userid in both tables. You should use LEFT JOIN instead of CROSS JOIN to return a row even if there is no row in data for the userid. 154 is just an example userid.)
Have a look at http://dev.mysql.com/doc/refman/5.5/en/join.html for information on the JOIN syntax.
users
| user_id | username | password | enabled |
|---------|----------|----------|---------|
| 1 | john | sgsd2gg | 1 |
| 2 | jane | sdshdhd | 0 |
users_data
|udata_id| user_id | some_column |
|--------|---------|-------------------|
| 1 | 1 | Some title |
| 2 | 2 | another title |
Since you haven't posted your table schema, I can't give you an exact solution. But supposing you have a users table and a users_data table, where users_data are owned by a user. You can do a join on the table to retrieve all the data.
SELECT * -- Don't select all fields unless you need it
FROM users U LEFT JOIN users_data UD ON U.user_id = UD.user_id
WHERE U.user_id = 1
This would pull all the records for user with an ID of 1. This is a very simplistic join, but it should give you an idea.
Here's an example that visually describes the different options you can use : SQL Join Differences
There are two tables table1 and table2
table1 has got two columns name and rank
table2 has got only one column name
names in table2 are almost listed in table1
I want compare two table and pull rank info from table1 and update/alter table2 with rank
table1
name | rank
-------------
john | 2
mathews| 5
keyn | 4
emly | 25
yancy | 8
stewart| 9
kim | 12
chris | 19
table2
name
-------
john
mathews
keyn
emly
yancy
stewart
I want update/insert rank details to table2 from table1
thats it and sorry for the confusion
Seem like you want to do something like this:
update table2,table1 set table2.rank=table1.rank where table2.name=table1.name
This will update the second table with ranks from the first table where the names are equal.
Then put auto increament field of table one in table2. and after this apply left join using these id and pull the info
refer this link
http://www.wellho.net/solutions/mysql-left-joins-to-link-three-or-more-tables.html