How to compare two rows in same table in mysql

More actions. I am looking for a sql query that will compare the Policy column values in all 5 rows and return those rows which have a value equal to atleast one other row. There are a couple of ways that you can handle this depending on what you want to do with the results. Where is the DDL for this table? What are the keys? What data types? What are the constraints? You really posted nothing. But worse than that, you seem to believe that there is such a thing as a generic, magical, universal "id" in RDBMS.

There is not.

Subscribe to RSS

We use keys and by definition, a key is a subset of the columns of a table such that they are unique for every row in that table. Guessing at what you might have meant to post, I would guess this:. This is one of the many many reasons that we ask people to post DDL.

If I was correct you would've put constraints on your table to assure this. Paulo de Jesus. ID, I. The original requires two scans of the table, once for the CTE and then once for the main query. The rewrite only requires one scan of the table. You must be logged in to reply to this topic. Login to reply. January 19, at pm For the table above I should get the following result set: 1 3 4 6 I would appreciate responses on how to write this query. Drew J.

January 20, at pm January 21, at am January 22, at am Viewing 6 posts - 1 through 6 of 6 total.By Steve Suehring, Janet Valade. With JOIN, the tables are combined side by side, and the information is retrieved from both tables. Tables are combined by matching data in a column — the column that they have in common. The combined results table produced by a join contains all the columns from both tables.

For instance, if table1 has two columns memberID and heightand table2 has two columns memberID and weighta join results in a table with four columns: memberID from table1heightmemberID from table2and weight. The two common types of joins are an inner join and an outer join. The difference between an inner and outer join is in the number of rows included in the results table. Inner join: The results table produced by an inner join contains only rows that existed in both tables.

Outer join: The combined table produced by an outer join contains all rows that existed in one table with blanks in the columns for the rows that did not exist in the second table. For instance, if table1 contains a row for Joe and a row for Sally, and table2 contains only a row for Sally, an inner join would contain only one row: the row for Sally. However, an outer join would contain two rows — a row for Joe and a row for Sally — even though the row for Joe would have a blank field for weight.

The results table for the outer join contains all the rows for one table. Clearly, the contents of the results table are determined by which table contributes all its rows, requiring the second table to match it.

The following query is an inner join:. In all three queries, table1 and table2 are the tables to be joined. You can join more than two tables.

In both queries, col1 and col2 are the names of the columns being matched to join the tables. The tables are matched based on the data in these columns. These two columns can have the same name or different names, but they must contain the same type of data. As an example of inner and outer joins, consider a Clothes catalog with two tables.

One table is Productwith the two columns Name and Type holding the following data:.

how to compare two rows in same table in mysql

The second table is Colorwith two columns Name and Color holding the following data:. You need to ask a question that requires information from both tables.

If you do an inner join with the following query:. Notice that only T-shirt appears in the results table — because only T-shirt was in both of the original tables, before the join.

On the other hand, suppose you do a left outer join with the following query:. You get the following results table, with the same four columns — Name from ProductTypeName from Colorand Color — but with different rows:.More actions. How to Compare Two Rows and find which are all the columns are got changed for the each part id. Lutz A pessimist is an optimist with experience. I don't understand your last requirement modified column names : How could this happen when you query just a single table?

Since I don't know enough about SyBase 15 I'd like to leave it for the folks knowing both systems. As a side note: it would help others if you could name the columns identifying a single row. Hi, do you mind to share how to do you do for this part? Even if you did use a windowing function, I don't see how you would identify what changed. You could do it with a trigger if you're changing a value in the table.

Are you just adding a new record with one or more columns having new values? You must be logged in to reply to this topic.

Login to reply.

how to compare two rows in same table in mysql

Ganapathi M. April 10, at am How to Compare Two Rows and find which are all the columns are got changed for the each part id actually i have around 20 columns in the table and need to list all the columns that are got changed. Here's a SQL Server solution. Hi LutzM, Thanks for your solution. This would cover items 1 to 3. April 10, at pm In my live table I have 25 columns.

March 1, at pm This post is 8 years old. Why not start your own post? Viewing 7 posts - 1 through 7 of 7 total.GeeksEngine is hosted by HostGator.

Self-join is normally used to represent hierarchical relationship or tree structure in a table. In Northwind employees table, an employee has a manager who is also an employee.

So we can use ReportsTo and EmployeeID to join the employees table to itself and find out the manager for each employee. Note that the SQL needs to end with semi-colon if you have multiple queries in the query window.

Most of the queries in the tutorials need Northwind MySQL database, you can download the database script on this page. Query result set - 8 rows returned:. Query result set - rows returned:. Happy Coding! Other tutorials in this category 1. Another Example for Outer Joins three tables 4. All Rights Reserved.

Subscribe to RSS

No portion may be reproduced without my written permission. Software and hardware names mentioned on this site are registered trademarks of their respective companies. Should any right be infringed, it is totally unintentional. Drop me an email and I will promptly and gladly rectify it. The query uses self-join where employees table joined with itself. Joined columns: Foreign key column ReportsTo in the employees table which is aliased as staff table.

Primary key column EmployeeID in the employees table which is aliased as manager table. EmployeeID. The where clause eliminates duplicate rows where emp1 is equal to emp2. Note that the first row and the second row are actually the same.

This kind of duplication is removed in Practice 3. EmployeeID as emp1a.This tip shows you different ways to compare data, datatypes and tables using SQL Server. I will show you different methods to identify changes.

Let's say that we have two similar tables in different databases and we want to know what is different. The T-SQL code generates 2 tables in different databases. The table names are the same, but the table in database dbtest02 contains an extra row as shown below:. The left join shows all rows from the left table "dbtest In this example, we are comparing 2 tables and the values of NULL are displayed if there are no matching rows. This can be done both ways to see if there are differences the other way around.

This query will just return the 3 matching rows. Except shows the difference between two tables the Oracle guys use minus instead of except and the syntax and use is the same. It is used to compare the differences between two tables. For example, let's see the differences between the two tables:. If we flip the tables around in the query we won't see any records, because the table in database dbtest02 has all of the records plus one extra.

This method is better than the first one, because if we change values for other columns like the type and cost, EXCEPT will notice the difference. Here is an example if we update id "" in database dbtest01 and change the cost from "40" to "1". If we update the records and then run the query again we will see these differences now:. There is a nice command line tool used to compare tables.

how to compare two rows in same table in mysql

This command line tool is used to compare tables. For more details, refer to this tablediff article. This feature is available in SQL Server and later. Basically it creates system tables that track the changes in your tables that you want to monitor. It does not compare tables, but it tracks the changes in tables. We are going to create a new table named dbo.

The difference is that the id is now an int instead of nchar 10 like the other tables. The query compares the data types from these two tables. We are comparing the table "article" with table "article2" and showing if any of the datatypes are different. Sometimes we need to make sure that two tables contain the same number of columns. To illustrate this we are going to create a table named "article3" with 2 extra columns named extra1 and extra The query compares the different columns between table "article" and "article3".

The different columns are extra1 and extra2. This is the result of the query:. Now let's compare the tables in database dbtest01 and dbtest The following query will show the different tables in dbtest01 compared with dbtestBy using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. For example, I have two table, supply and demand with same columns.

For each rows in the supply table, I want to know how many demand match with these, and vice versa. I'm going to attempt an answer, but it's a very vast question, especially if you want to consider performances if both tables are big, you'll need a different solution altogether. One way of doing this would be to create a table, e.

Score would be 0, 1, 2 or 3, based on your example, or a percentage number of fields in common. This way you can easily and quickly query this table. Now how to fill this table? You could do it with a script in whatever scripting language you are using, or in pure SQL possibly with a trigger if you feel like it. For example something like this should work:. Note that the join has no join condition, so every rows combination will be processed by MySQL to calculate every possible scores.

It can take quite a while! Learn more. How to match two table in mysql Ask Question. Asked 4 years, 7 months ago. Active 4 years, 7 months ago. Viewed times. I want to ask if there is a "pratical" solution to match two table You should read about joins in SQL. Edit your question with sample data and desired results. A SQL Fiddle can also help communicate what you want to do. Active Oldest Votes. Sign up or log in Sign up using Google.

Sign up using Facebook.

How to compare 2 records of same table?

Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. The Overflow How many jobs can be done at home? Socializing with co-workers while Social distancing. Featured on Meta. Community and Moderator guidelines for escalating issues via new response…. Feedback on Q2 Community Roadmap.

Triage needs to be fixed urgently, and users need to be notified upon….Summary : in this tutorial, you will learn how to compare two tables to find the unmatched records. In data migration, we often have to compare two tables to identify a record in one table that have no corresponding record in another table.

For example, we have a new database whose schema is different from the legacy database. To check the data, we have to compare two tables, one in the new database and one in the legacy database and identify the unmatched records. The following steps compare two tables and identify the unmatched records:.

TSQL: Compare Tables

First, use the UNION statement to combine rows in both tables; include only the columns that need to compare. The returned result set is used for the comparison. Second, group the records based on the primary key and columns that need to compare. Fifth, execute the query to compare the values of title column in both tables again. The new row, which is the unmatched row, should return. In this tutorial, you have learned how to compare two tables based on specific columns to find the unmatched records.

More About Us. The following steps compare two tables and identify the unmatched records: First, use the UNION statement to combine rows in both tables; include only the columns that need to compare. Was this tutorial helpful? Yes No.