We can use the optional column constraint IDENTITY to provide a unique, incremental value for that column. Table constraints are identified by the CONSTRAINT keyword and can be used to implement various constraints described below. To illustrate, we will use the SQL statement CREATE TABLE EMPLOYEES to create the employees table with 16 attributes or fields. The column constraint NOT NULL indicates that a value must be supplied when a new row is created. The column constraint NULL indicates that null values are allowed, which means that a row can be created without a value for this column. The Optional ColumnConstraints are NULL, NOT NULL, UNIQUE, PRIMARY KEY and DEFAULT, used to initialize a value for a new record. Image – Variable-length binary data with a maximum length of 2^31 – 1 (2,147,483,647) bytes Optional Column Constraints Varbinary –Variable-length binary data with a maximum length of 8,000 bytes Text –Variable-length non-Unicode data with a maximum length of 2^31 – 1 (2,147,483,647) charactersīinary –Fixed-length binary data with a maximum length of 8,000 bytes Varchar –Variable-length non-Unicode data with a maximum of 8,000 characters Smalldatetime –Date and time data from January 1, 1900, through June 6, 2079, with an accuracy of one minuteĬhar –Fixed-length non-Unicode character data with a maximum length of 8,000 characters Real –Floating precision number data from -3.40E + 38 through 3.40E + 38ĭatetime –Date and time data from January 1, 1753, to December 31, 9999, with an accuracy of one-three-hundredths of a second, or 3.33 milliseconds Smallmoney –Monetary data values from -214,748.3648 through +214,748.3647, with accuracy to one-ten-thousandth of a monetary unitįloat –Floating precision number data from -1.79E + 308 through 1.79E + 308 Uniqueidentifier –A globally unique identifier (GUID) Smallint –Integer data from 2^15 (-32,768) through 2^15 – 1 (32,767)ĭecimal –Fixed precision and scale numeric data from -10^38 -1 through 10^38 The data type, as described below, must be a system data type or a user-defined data type. Many of the data types have a size such as CHAR(35) or Numeric(8,2).īit –Integer data with either a 1 or 0 value Some examples of ColumnNames are FirstName and LastName. The ColumnName must be unique within the table. Each field in the CREATE TABLE has three parts (see above): Tablename is the name of the database table such as Employee. The general format for the CREATE TABLE command is:ĬolumnName, Datatype, Optional Column Constraint,
Once the database is created, the next step is to create the database tables. The SQL statement CREATE is used to create the database and table structures.Ī new database named SW is created by the SQL statement CREATE DATABASE SW. The major SQL DDL statements are CREATE DATABASE and CREATE/DROP/ALTER TABLE.
#Create function psequel update#
In Chapter 16, we will use SQL as a data manipulation language ( DML) to insert, delete, select and update data within the database tables. In this chapter, we will focus on using SQL to create the database and table structures, mainly using SQL as a data definition language ( DDL). Perform complex queries to transform raw data into useful information.Perform basic data management chores (add, delete and modify).Create the database and table structures.In a DBMS, the SQL database language is used to: Many of the currently available relational DBMSs, such as Oracle Database, Microsoft SQL Server (shown in Figure 15.1), MySQL, IBM DB2, IBM Informix and Microsoft Access, use SQL.
#Create function psequel software#
Then in the late 1970s, Relational Software Inc., which is now Oracle Corporation, introduced the first commercially available implementation of SQL, Oracle V2 for VAX computers. The initial version, called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM’s quasi-relational database management system, System R. SQL was initially developed by IBM in the early 1970s (Date 1986). Structured Query Language (SQL) is a database language designed for managing data held in a relational database management system.
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