Introduction to Update SQL Commands
Every available RDBMS database basically supports SQL (Structured query language) statements or commands for executing any developer query from the storing data in the corresponding database. In addition, every database may support or need some update specific SQL command kind language for executing any kind of specific query on the storing data in those databases.
Basic Update SQL Commands
There are many updated SQL commands available for the various databases, especially for fetching, inserting, deleting, or truncating kind of data manipulation level of the task. Some of the basic update SQL commands are mentioned below:
1. Alter table
Basically, use for altering one existing table column definition, adding one new column, or deleting one already added column. Alter table column can also be used in the case of rename table as well.
2. Create a table
It is used to create a new table with a specific definition, create a table can use for some new table with default tablespace, and use some define tablespace on a creating new table need to define the same with the create statement.
3. Create a view
Using this command, we can able to create one view. Suppose there is a specific query that took a long time to execute; in that case, we can define that specific query as a temporary table and create one new view with this temporary table executed data. Now calling the view directly except this query execution it will give a result much faster than usual. Create view command actually helping to create the same.
It is used for deleting the table, specific column of the table, specific row of the table, or entire data inside the table. There are normally three kinds of delete available in update SQL commands, delete by using some cursor commands, and delete some specific key column data by mentioning in the cursor. Delete by some command, where someone can delete some key data with a specific dynamic condition; it can delete one specific or multiple rows as well based on the provided condition. Delete by using some language command, here also again some condition of specific language which helps to remove one or multiple rows at a time.
It is used for insert commands; someone can able to insert one or multiple rows in the table. There are two kinds of critical inserts available in the case of SQL. One is inserted rows in a table or view by using some dynamic condition. Here someone can insert data in the table based on some dynamic condition mentioned in the query. And another one is inserted into the table or view based on some language command. In this case, an insert can be done based on some language conditions mentioned in the command.
The update command is mainly used for updating some of the existing rows in a table. Three kinds of update available in SQL by using cursor one kind of positional update, by using the dynamic command, one kind of dynamic update based on the mentioned query, by using language command, it is also a dynamic update but based on the specific language.
Several other popular update SQL commands have also been used by the developer, which is not very basic commands but working with SQL more; those Update SQL commands are very much required to execute. Some of those kinds of requiring intermediate update SQL commands are mentioned below:
1. Begin transaction
Begin transaction is for managing or mention the starting point of the user-created transaction management. For example, suppose someone willing to execute multiple data manipulation query but willing to commit the same query one time, in that case, begin transaction need to mention for identifying starting of those DML statements.
2. Commit transaction
It was basically committing the entire transaction into the database. As mentioned earlier, someone is willing to commit an entire DML statement one time without any individual commitment. In that case, where they will mention the ‘commit transaction’ command, it will commit the entire DML execution in between transaction boundary means from begin to commit.
3. Create an index
Create one specific index for the table, sometimes on some specific useful column. The index has been created on some key columns of the table where those columns are very much useful in terms of application logic.
4. Truncate table
Truncating one table data, but it will never drop the table structure.
5. Rollback transaction
It also does the same thing like commit; it normally rollbacks the entire transaction in between define transaction boundaries.
Still, some of the critical tasks need to be done by the SQL command users frequently. Those tasks also have some advanced kind of commands that need to be executed, which are mainly used by some of the managerial people for granting or revoking some access to the specific user, dropping some of the critical table structure, providing permission for accessing the specific table in the database, etc. Those advanced kinds of update SQL commands are below:
1. Drop index
Dropping the existing created index with structure from the database. It is some architectural decision to drop one index from a specific table that can have multiple impacts. So dropping access is normally given to some specific key people of one project.
2. Drop table
Dropping one existing define table with structure from the database. Dropping one table from the database means the table will entirely remove.
Granting an entire table or database for some specific critical users.
Revoking some critical accesses for some specific users.
Providing access to one existing database.
Tips and Tricks to Use SQL Commands Update
Some common users who are very frequently using SQL queries, they normally use some of the tips and tricks for utilizing SQL commands output in a proper way. Those kinds of tricks normally solve some user-specific queries and display execution output for understanding the same properly. Some of the very commonly used key tricks are:
1. SELECT command optimization
Some of the developers common attitudes are to use ‘select *’ at the time of fetching data from any specific database. Whereas using select with specific mention column name always be helpful for returning data smoothly. It is avoiding fetching a lot of unnecessarily column details.
2. Avoiding subqueries at the time of joining
Common developer normal attitude of using subqueries at the time of performing joining between two tables. But subqueries always returning slow responses any time than proper joining. So avoid subqueries will always be helpful at the time of writing proper SQL queries.
Any kind of SQL query has to be understood properly for working in the IT industry. Normally maximum SQL queries are common for the entire database. Some of the databases are supporting some critical changes in the update SQL commands, but the common features of those executions are normally the same.
This has been a guide to Update SQL Commands. Here we have discussed basic, immediate as well as advanced Update SQL Commands along with tips & tricks to use commands. You may also look at the following article to learn more –