Note:This command is not supported by our online SQL editor as it is based on SQLite. Auto Increment Primary Key It is a common practice to automatically increase the value of the primary key whenever a new row is inserted. For example, SQL Server -- use IDENTITY(x, y) to auto increme...
Here, the SQL command creates an index namedcollege_indexon theCollegestable using thecollege_codecolumn. SQL CREATE INDEX Syntax The syntax of the SQLCREATE INDEXstatement is: CREATEINDEXindex_nameONtable_name (column_name1, column_name2, ...); Here, index_nameis the name given to the in...
Here, the SQL command adds thephoneandagecolumns to theCustomerstable. Note:Since our compiler uses SQLite, it does not support adding multiple columns withALTER TABLE. However, many other database management systems support this command. Rename Column in a Table We can rename columns in a tabl...
TheTOPkeyword is used in place ofLIMITwith the following database systems: SQL Server MS Access Let's look at an example. SELECTTOP2first_name, last_nameFROMCustomers; Here, the SQL command selectsfirst_nameandlast_nameof the first2rows. We can also use*withTOPto select all columns. SELE...
In Oracle and SQL Server CREATETABLECompanies (idintNOTNULLPRIMARYKEY,namevarchar(50), addresstext, emailvarchar(50), phonevarchar(10) ); To learn more, visitSQL PRIMARY KEY. Define constraints while creating a table We can also add different types of constraints while creating a table. For ...
SQL Server ALTERTABLECollegesALTERCOLUMNcollege_idINT; Oracle ALTERTABLECollegesMODIFY(college_idNULL); MySQL ALTERTABLECollegesMODIFYcollege_idINT; PostgreSQL ALTERTABLECollegesALTERCOLUMNcollege_idDROPNOTNULL; Here, we have used theALTER TABLEcommand in various database systems to remove theNOT NULLconst...
In this SQL tutorial series, we will learn about SQL in detail. We will cover any SQL command differences among MySQL, Oracle, SQL Server, Postgres, and other commonly used database systems. Previous Tutorial: Getting Started with SQL