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What is Update Query in SQL? How to Update (Column Name, Table, Statement, Values)

If you wanted to become a successful SQL programmer then working with tables is common and you have to face multiple problems too. Before you start programming in the workplace, you must have a deep understanding of SQL basic commands how to use them to manage or store data in the database.

How to use an update query in SQL?

  • First of all, download one database management application i.e. MySQL.
  • Once it is downloaded, understand the hierarchy of the database.
  • Make a study on fields that you want to add in the table.
  • Now write a query to update data in the table either it is a column, a particular field, a statement, or values etc.

We will discuss the Update query in rest of the article below with detailed explanation.

The beauty of SQL is that anyone working within a Company can use this language to store or manage data. If you wanted to pull specific details related to the employee in a table then it can be quickly done with the SQL. For an e-commerce Firm, the owner wanted to keep a close eye on purchases, and profits of the Company, even then SQL works simply great. There are a plenty of similar examples that can explain you the importance of language.

For example, you have to open a large dataset a plenty of times just to complete a simple task but the same task can be made faster with commands and queries in SQL. In brief, SQL works on data chunks and analyzing the database based on the commands you are putting within a statement. SQL Server Curriculum

What is an Update Query in SQL?

Before you start working on the table, you should be accustomed to the database and its hierarchy. If you are working with multiple databases then start with the location zero from where you want to work with. For this purpose, you can use the “Show Databases” command. Once you are sure on which database you have to work with, the next step is to find fields that can be pulled with the help of commands or queries in SQL.

Read: What Is A Data Warehouse, And Why You Need It?

One of the most popular examples when working with SQL is an Update command that is used to update the existing records within a Table.  This is an action query that can be applied to a set of records based on conditions you specify. This is taken as one of the most powerful features of RDBMS because you have the flexibility to modify multiple records together. A depth understanding of the Update Query helps you in improving the performance of a database application instead of performing all changes one by one manually in the code. Also, the maintenance of changes is much easier than you ever think of.

With update command in SQL, you can work on multiple records together and WHERE clause in between to specify some condition. Here, are the possible uses of Update Query within a database –

  • It can be used to set the same values for all the records.
  • A value from another table to your table.
  • A value from the field to the linked table.
  • A value derived from some expression.
  • One VBA function where field values can be used as parameters
  • One customized VBA function where parameters could be set NULL

Facts to Consider while using an Update query in SQL

  • The update query is useful when you wanted to modify multiple records in a single table or multiple tables.
  • The query will not process any result set but you cannot undo operations once it has been changed. If you wanted to do so then find the changes first with the SELECT query, apply the same criteria, and run the update query again.
  • Along with the ‘update’ command, you should use ‘view’ command too, so that you can review the changes wherever you have been made it.
  • Don’t forget to maintain the backup copies of all the tables. In case, you have modified or updated some fields wrongly then the same can be covered from the backup files.
  • To avoid the situations where field name matches each other, use a “RESERVED” keyword 'to make them unique or add brackets along.

How to update values in SQL?

The update command is used to modify data that is already added to the database. You don’t have to re-insert the new data in the table. Here, is the comprehensive guide that will make you familiar with the syntax and you will learn how to update values or fields in SQL with a few simple steps. SQL Server quiz Here is the quick syntax how update statement looks like in SQL –


UPDATE table_ name SET column1 = value1, column2 = value2, ... Column n = value n [WHERE condition];

The syntax involves the name of the table you want to update, the columns and their respective values with a where clause to specify conditions. The Update Statement in SQL starts with the Update keyword and it sends information to Oracle that you are interested in updating something. Further, you need to give the name of the table. Keep in mind that you could give only a single name here. For another table, you have to write one more UPDATE statement.

In the next line, you can see the keyword “SET", then give the column name. This will give the information about the column that you want to update. After the keyword and column name, add “=” to assign the value.

Read: Delete vs Truncate SQL Server – What are the Differences?

How to Update multiple columns in SQL?

In SQL, the UPDATE statement is used to modify multiple columns together and the syntax for update statement in SQL is given below


SET column1 = value1, column2 = value2, ... Column n = value n 

In the syntax, you can see the SET keyword and column name is given afterward. Add the possible number of columns here and their respective values too that you wanted to modify. Further, append one where clause to restrict the modification. For example, change the column value whose salary is greater than 5000 or more. The best part is that you don’t have to use SET keywords multiple time even if you are modifying values multiple times. In brief, you need SET keyword only once.

Where clause is optional but it makes your changes more meaningful and up to the mark. Smart SQL developers love to add this to avoid any mistakes. Without a WHERE clause, almost every row will be updated, you don’t want this probably. To modify only a selected number of records, you should use where clause smartly. free SQL Server demo Where clause works very much similar to the SELECT command and values will be updated only when the condition is set to TRUE. To understand the concept deeply, take a working example and add the values in the UPDATE statement. Here in this example, the name of the table is “employee” and you wanted to increase the salary of each employee by 10K whose department ID is 4. So, how to write it as an Update statement –


UPDATE employee SET salary = salary + 10000 WHERE department_ id = 4; 

It will automatically add an amount of Rs. 10,000 to the employee salaries whose department ID is 4. As soon as the query will run, data will be updated automatically in the table. So, now you must be clear how to use UPDATE command in SQL to modify multiple fields together and its significance too.

Read: How to Become a SQL Database Administrator?

Update Query Fails to run in SQL

If you are not able to update any table then, first of all, check the permission sets of the table if you have the right to edit it or not. To check, simply open the table and try to edit any field manually. Still, you are not successful then there could be a plenty of reasons for the error as mentioned below –

  • The administrator has set READ ONLY permission for the file and none of the data can be modified until you are not given permission for the same.
  • In case, you are using ACCESS WORKGROUP SECURITY then you are not allowed to edit the data. The only solution is to log in as an administrator and set the proper rights who can edit the data and who should be restricted instead of giving the same permissions to all added users.
  • If the table is linked then it is generally not allowed to edit by the owner.
  • If the table does not have any primary key then you cannot edit it on your own.

Verdict

Great! So, what we have concluded from the discussion of Update query in the blog, Rarely, there is need of updating the entire table but you have to work with columns or fields when specific conditions are satisfied. If you don’t want to turn your data in a mess then make sure where to use UPDATE command and how to use it. This blog will surely help in using the command successfully otherwise you can take the help of our expert educators at JanBask Training to discuss the doubts in detail.

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