![]() VALUES( 'New Product', 900, 1000) Code language: SQL (Structured Query Language) ( sql ) INSERT INTO products(product_name, list_price, discount) The following statement violates the CHECK constraint because the discount is higher than the list price. The CHECK constraint ensures that list price is always greater or equal to discount and both discount and list price are greater or equal to zero. List_price >= 0) Code language: SQL (Structured Query Language) ( sql ) In this example, the CHECK constraint is defined at the table level: CHECK (list_price >= discount AND The following statement creates a new table named products: CREATE TABLE products (ĭiscount DECIMAL ( 10, 2) NOT NULL DEFAULT 0, VALUES( 'John', 'Doe', '(408)-123-456') Code language: SQL (Structured Query Language) ( sql ) 2) Using SQLite CHECK constraints at the table level example The following statement should work because the value in the phone column has 13 characters, which satisfies the expression in the CHECK constraint: INSERT INTO contacts(first_name, last_name, phone) The reason was that the phone number that you attempted to insert just has 9 characters while it requires at least 10 characters. Here is the error message: Result: CHECK constraint failed: contacts VALUES( 'John', 'Doe', '408123456') Code language: SQL (Structured Query Language) ( sql ) If you attempt to execute the following statement, you will get a constraint violation error: INSERT INTO contacts(first_name, last_name, phone) This CHECK constraint ensures that the values in the phone column must be at least 10 characters. In the contacts table, the phone column has a CHECK constraint: CHECK ( length(phone) >= 10) Phone TEXT NOT NULL CHECK ( length(phone) >= 10) The following statement creates a new table named contacts: CREATE TABLE contacts ( 1) Using SQLite CHECK constraint at the column level example Let’s take some examples of using the CHECK constraints. Note that the expression of a CHECK constraint cannot contain a subquery. If the result is a non-zero value or NULL, it means no constraint violation occurred. If the result is zero, then a constraint violation occurred. In this syntax, whenever a row is inserted into a table or an existing row is updated, the expression associated with each CHECK constraint is evaluated and returned a numeric value 0 or 1. The following statement shows how to define a CHECK constraint at the column level: CREATE TABLE table_name(Ĭode language: SQL (Structured Query Language) ( sql )Īnd the following statement illustrates how to define a CHECK constraint at the table level: CREATE TABLE table_name( SQLite allows you to define a CHECK constraint at the column level or the table level. The CHECK constraints allow you to define additional data integrity checks beyond UNIQUE or NOT NULL to suit your specific application. If the values do not meet the criteria defined by the expression, SQLite will issue a constraint violation and abort the statement. SQLite CHECK constraints allow you to define expressions to test values whenever they are inserted into or updated within a column. These expressions are used in various data manipulations.Summary: in this tutorial, you will learn how to use SQLite CHECK constraint to validate data before insert or update. Sqlite> SELECT COUNT(*) AS "RECORDS" FROM COMPANY ĭate Expressions returns the current system date and time values. There are several built-in functions such as avg(), sum(), count(), etc., to perform what is known as aggregate data calculations against a table or a specific table column. Following is a simple example showing the usage of SQLite Numeric Expressions. Here, numerical_expression is used for mathematical expression or any formula. ![]() SELECT numerical_expression as OPERATION_NAME These expressions are used to perform any mathematical operation in any query. Sqlite> SELECT * FROM COMPANY WHERE SALARY = 10000 Following is the syntax −Ĭonsider COMPANY table with the following records −įollowing is a simple examples showing the usage of SQLite Boolean Expressions − SQLite Boolean Expressions fetch the data on the basis of matching single value. SyntaxĬonsider the basic syntax of the SELECT statement as follows −įollowing are the different types of SQLite expressions. You can also use to query the database for a specific set of data. SQL expressions are like formulas and they are written in query language. An expression is a combination of one or more values, operators, and SQL functions that evaluate to a value.
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