How can I get distinct values from multiple tables in MySQL?

How can I get distinct values from multiple tables in MySQL?

DISTINCT on multiple columns

1. Sample Select statement.
2. Select with distinct on two columns.
3. Select with distinct on three columns.
4. Select with distinct on all columns of the first query.
5. Select with distinct on multiple columns and order by clause.
6. Count() function and select with distinct on multiple columns.

How do you find unique records from a set of tables?

The SQL SELECT DISTINCT Statement The SELECT DISTINCT statement is used to return only distinct (different) values. Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.

Can I SELECT from multiple tables?

From multiple tables To retrieve information from more than one table, you need to join those tables together. This can be done using JOIN methods, or you can use a second SELECT statement inside your main SELECT query—a subquery.

How do I SELECT unique records in MySQL?

To get unique or distinct values of a column in MySQL Table, use the following SQL Query. SELECT DISTINCT(column_name) FROM your_table_name; You can select distinct values for one or more columns. The column names has to be separated with comma.

What is difference between unique and distinct in SQL?

The UNIQUE keyword in SQL plays the role of a database constraint; it ensures there are no duplicate values stored in a particular column or a set of columns. On the other hand, the DISTINCT keyword is used in the SELECT statement to fetch distinct rows from a table.

How do I SELECT distinct rows in MySQL?

How do I get unique records in MySQL?

You can use the DISTINCT command along with the SELECT statement to find out unique records available in a table. mysql> SELECT DISTINCT last_name, first_name -> FROM person_tbl -> ORDER BY last_name; An alternative to the DISTINCT command is to add a GROUP BY clause that names the columns you are selecting.

How do I write a SELECT query for multiple tables?

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.

Can you SELECT from multiple tables in SQL?

In SQL we can retrieve data from multiple tables also by using SELECT with multiple tables which actually results in CROSS JOIN of all the tables. The resulting table occurring from CROSS JOIN of two contains all the row combinations of the 2nd table which is a Cartesian product of tables.

How do I SELECT multiple columns from different tables in SQL?

Is GROUP BY or distinct faster?

DISTINCT is used to filter unique records out of all records in the table. It removes the duplicate rows. SELECT DISTINCT will always be the same, or faster than a GROUP BY.

Is SELECT distinct faster than GROUP BY?

How does distinct work in MySQL?

If you put more than one expression in the DISTINCT clause, the query will retrieve unique combinations for the expressions listed. In MySQL, the DISTINCT clause doesn’t ignore NULL values. So if you are using the DISTINCT clause in your SQL statement, your result set will include NULL as a distinct value.

How do I SELECT different columns in different tables in MySQL?

“how to select multiple columns from different tables in mysql” Code Answer

1. — MySQL.
2. — t1 = table1.
3. — dt2 = column of table.
4. SELECT t1. dt2, t2. dt4, t2. dt5, t2. dt3 #get dt3 data from table2.
5. FROM table1 t1, table2 t2 — Doesn’t need to have t1, or t2.
6. WHERE t1. dt2 = ‘asd’ AND t2. dt4 = ‘qax’ AND t2. dt5 = 456.
7. ​

What we can use instead of distinct in SQL?

GROUP BY is intended for aggregate function use; DISTINCT just removes duplicates (based on all column values matching on a per row basis) from visibility. If TABLE2 allows duplicate values associated to TABLE1 records, you have to use either option.

Is SELECT distinct expensive?

In a table with million records, SQL Count Distinct might cause performance issues because a distinct count operator is a costly operator in the actual execution plan.

Is SQL distinct slow?

Very few queries may perform faster in SELECT DISTINCT mode, and very few will perform slower (but not significantly slower) in SELECT DISTINCT mode but for the later case it is likely that the application may need to examine the duplicate cases, which shifts the performance and complexity burden to the application.

How to concatenate multiple columns in MySQL?

CONCAT. This function is used to concatenate multiple columns or strings into a single one.

CONCAT_WS. The CONCAT_WS () function not only adds multiple string values and makes them a single string value.

Using them in WHERE CLAUSE. You can use both of them in WHERE CLAUSE for selection based on condition.

Conclusion.

How to get all columns from a SELECT DISTINCT query?

Aliases and identifiers are case-insensitive by default. To preserve case,enclose them within double quotes ( ” ).

Without an ORDER BY clause,the results returned by SELECT are an unordered set.

SELECT can be used not only as an independent statement,but also as a clause in other statements,for example INSERT INTO SELECT …; .

How to select last row in MySQL?

A) Using MySQL LAST_INSERT_ID () function to get value when inserting one row into a table. First,create a new table named messages for testing.

B) Using MySQL LAST_INSERT_ID () function to get value when inserting multiple rows into a table.

C) Using MySQL LAST_INSERT_ID () function in a stored procedure.

How to order MySQL rows by multiple columns?

Data Source

Order by. This sorts your MySQL table result in Ascending or Descending order according to the specified column.

Using with multiple columns. Define your multiple column names in ORDER BY clause separated by a comma (,).

Conclusion. Order by clause is used with the SELECT query to arrange results in a specific order.