Top 20 SQL Commands to Master

Command # 1—Alias

This command can be used to temporarily rename a table. The new “alias” that a table is assigned, however, will only exist within the transaction that is currently being run.

Command # 2—Alter Table

Users rely on the “alter table” command to modify a table’s structures. While many people find this command helpful, there are some limitations involved with “alter table.” For example, databases will not let you alter a table if the existing data would result in a conflict.

Command # 3—And

“And” is a command that lets a user combine two conditions. It is critical to understand that both conditions used must be true for that rows that are combined. The command is used as a building block for many other commands in SQL.

Command # 4—Average

Users rely on the “average” command to return an average value for a selected area. This command plays an important role for users who want to quickly analyze data while reducing the error associated with performing manual calculations.

Command # 5—Between

The “between” command helps users to filter information between an established range of data. This command is particularly helpful in finding specific types of data quickly.

Command # 6—Create Table

The simple but beneficial command of “create table” allows users to create tables in a database. There are many other types of commands in SQL based on this command.

Command # 7—Delete

Users rely on “delete” to remove records entirely from a row. While this command is often helpful, it can result in negative consequences if users are not careful.

Command # 8—Drop Table

“Drop table” is similar to the “delete” command, but “drop table” removes every single record in a database as well as the table. Users should make sure to use this command sparingly because it will result in the loss of significant amounts of data.

Command # 9—Insert

The “insert” command has some powerful uses and can be used to insert sections of a database into other areas. There is some limitation, however, to “insert.” For example, users must make sure to follow any necessary table constraints or the command will not work correctly.

Command # 10—Join

“Join” is used to join related data that is stored in multiple tables.

It is important for users to understand that there are several different types of “join” commands which include:

• “inner join” which returns rows with a match in both tables
• “left” or “outer join” which returns rows from the left table with any matches from the right table
• “right” or “outer join” which returns from the right table with any matches from the left table, and
• “full” or “outer join” which returns any records with a match in either table

Command # 11—Maximum and Minimum

The “maximum” and “minimum” functions are separate commands but very comparable to one another. The “maximum” command returns the largest value in a column, while the “minimum” function returns the small value in a column. These commands help users manage a group of numbers much more quickly.

Command # 12—Order

“Order” is a command that can be used to sort results that are returned. While this is one of the easiest commands to use, many people discover that the command is particularly helpful because not all queries returned data in an organized manner.

Command # 13—Or

Users can use the “or” command to include rows when only one of two commands are met. This command is the building block of many larger commands in SQL.

Command # 14—Round

The “round” command is used to round the values of a selected column to a specified number of decimal places. This tool is particularly helpful when users want to analyze a group of numbers quickly.

Command # 15—Select

This simple command is critical in understanding a number of other SQL commands. Used to select data from a database, the command underpins a large number of other commands used in SQL. There are even specific codes that can be entered in SQL to ensure that only specific columns in a database are retrieved.

Command # 16—Sum

“Sum” provides the invaluable feature of returning the sum of all the values in a column. This command saves users a substantial amount of time that would have otherwise been spent tallying together a series of numbers in a table.

Command # 17—Union

“Union” is a command that lets users join rows to one another. This command is different join because union enables a user join unrelated rows provided that they have columns of the same number and number.

Command # 18—Update

The “update” command can be particularly beneficial after inserting data because it helps users to organize rows. There are some limitations, however, on the constraints that users have in updating conditions.

Command # 19—Where

While “select” is a powerful command to retrieve data, users who want to filter results further are able to use the “where” command. This powerful command allows users to apply conditions to select.

Command # 20—With

The “with” command lets users store the results of a query in a temporary table. Some users know the “with” command as common table expression (CTE).

Advanced Skills

The commands that have so far been described in this article are considered fundamental SQL skills.

There are also advanced SQL skills that users can develop through enrollment in an SQL class, which include the following:

• Triggers refer to certain programs, which are automatically executed when certain requirements occur. Triggers provide users with numerous benefits including auditing and preventing invalid operations.