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Can SQL join on multiple columns?

Jeremy Anderson

Can SQL join on multiple columns?

If you’d like to get data stored in tables joined by a compound key that’s a primary key in one table and a foreign key in another table, simply use a join condition on multiple columns. In one joined table (in our example, enrollment ), we have a primary key built from two columns ( student_id and course_code ).

How do I combine multiple columns into one in MySQL?

How to Combine Columns Values Into a New Column in MySQL

  1. fullName = CONCAT(firstName, ‘ ‘, lastName)
  2. ALTER TABLE table_name ADD COLUMN fullName VARCHAR(100);
  3. UPDATE table_name SET fullName = CONCAT(firstName, ‘ ‘, lastName);
  4. CREATE TRIGGER insert_trigger BEFORE INSERT ON table_name FOR EACH ROW SET new.

How do I join two tables in different columns in SQL?

Multiple tables can be merged by columns in SQL using joins. Joins merge two tables based on the specified columns (generally, the primary key of one table and a foreign key of the other). Below is the generic syntax of SQL joins. USING (id);

How do I join two columns in SQL Server?

SQL Server CONCAT() Function

  1. Add two strings together: SELECT CONCAT(‘W3Schools’, ‘.com’);
  2. Add 3 strings together: SELECT CONCAT(‘SQL’, ‘ is’, ‘ fun!’ );
  3. Add strings together (separate each string with a space character): SELECT CONCAT(‘SQL’, ‘ ‘, ‘is’, ‘ ‘, ‘fun!’ );

How do I merge two columns in a single column in SQL?

To merge two columns value as one, we can concatenate it as one and use alias for that value. This is the simplest way to do it. Here the combination of FirstName and LastName is separated by a blank space and given as FullName.

How do I concatenate two columns in SQL with a hyphen?

Do it with two concats: select concat(concat(amt, ‘-‘), endamt) as amount from mstcatrule; concat(amt,’-‘) concatenates the amt with the dash and the resulting string is concatenated with endamt .

How do I get multiple columns from multiple tables in SQL?

Example syntax to select from multiple tables:

  1. SELECT p. p_id, p. cus_id, p. p_name, c1. name1, c2. name2.
  2. FROM product AS p.
  3. LEFT JOIN customer1 AS c1.
  4. ON p. cus_id=c1. cus_id.
  5. LEFT JOIN customer2 AS c2.
  6. ON p. cus_id = c2. cus_id.

What is the difference between UNION and join?

The difference lies in how the data is combined. In simple terms, joins combine data into new columns. If two tables are joined together, then the data from the first table is shown in one set of column alongside the second table’s column in the same row. Unions combine data into new rows.

Is join the same as outer join?

In SQL, a join is used to compare and combine — literally join — and return specific rows of data from two or more tables in a database. An inner join finds and returns matching data from tables, while an outer join finds and returns matching data and some dissimilar data from tables.

How to join tables on multiple columns in a database?

You want to join tables on multiple columns by using a primary compound key in one table and a foreign compound key in another. Example: Our database has three tables named student , enrollment , and payment .

What is the use of join in MySQL?

A join is a method of linking data between one or more tables based on values of the common column between the tables. MySQL supports the following types of joins: Inner join; Left join; Right join; Cross join; To join tables, you use the cross join, inner join, left join, or right join clause for the corresponding type of join.

What is the difference between left and right join in MySQL?

MySQL RIGHT JOIN clause The right join clause is similar to the left join clause except that the treatment of tables is reversed. The right join starts selecting data from the right table instead of the left table. The right join clause selects all rows from the right table and matches rows in the left table.

What is a cross join in MySQL?

The cross join is useful for generating planning data. For example, you can carry the sales planning by using the cross join of customers, products, and years. In this tutorial, you have learned various MySQL join statements, including cross join, inner join, left join, and right join, to query data from two tables. Was this tutorial helpful?