Updating a select
Updating a select - dating your ex ebook review
In both cases, you use the SQL statement INSERT INTO to accomplish the task.INSERT INTO statements are commonly referred to as append queries.
Figure 1 shows the result of dragging and dropping the EMPLOYEE table into the Oracle SQL Developer SQL Worksheet.Perusal of your schema diagram reveals that employee data is in a table called EMPLOYEE.You can then use the following SELECT statement: The SELECT list in the above statement specifies three columns—listing the first name, last name, and date of hire for every employee contained in the EMPLOYEE table, which is specified in the FROM clause.To remove all the records from a table, use the DELETE statement and specify which table or tables from which you want to delete all the records. Syntax update statement ::= Description of the illustration update_Keyword and Parameter Description alias Another (usually short) name for the referenced table or view, typically used in the contains references to columns in the table being updated, the references are resolved in the context of the current row.To add one record to a table, you must use the field list to define which fields to put the data in, and then you must supply the data itself in a value list. For example, the following statement will insert the values "1", "Kelly", and "Jill" into the Customer ID, Last Name, and First Name fields, respectively.
To add many records to a table at one time, use the INSERT INTO statement along with a SELECT statement.
To modify the data that is currently in a table, you use the UPDATE statement, which is commonly referred to as an update query.
The UPDATE statement can modify one or more records and generally takes this form: To delete the data that is currently in a table, you use the DELETE statement, which is commonly referred to as a delete query. The DELETE statement can remove one or more records from a table and generally takes this form: The DELETE statement does not remove the table structure—only the data that is currently being held by the table structure.
(To specify multiple columns in a SELECT list, you separate the column names with commas; a good practice is to insert a space after each comma for readability.) When the above statement is executed, the is a list of all the values found in the first_name, last_name, and hire_date columns of the EMPLOYEE table, as shown in Listing 1.
Code Listing 1: Code Listing 1: SELECT statement result for three columns SELECT first_name, last_name, hire_date FROM employee FIRST_NAME LAST_NAME HIRE_DATE —————————— ——————————————— ————————————— Frances Newton 14-SEP-05 Emily Eckhardt 07-JUL-04 Donald Newton 24-SEP-06 Matthew Michaels 16-MAY-07 SELECT * FROM employee EMPLOYEE_ID FIRST_NAME LAST_NAME HIRE_DATE SALARY MANAGER DEPARTMENT_ID ——————————— —————————— ————————— —————————— —————— ——————— ————————————— 37 Frances Newton 2005-09-14 75000 28 Emily Eckhardt 2004-07-07 100000 1234 Donald Newton 2006-09-24 80000 28 10 7895 Matthew Michaels 2007-05-16 70000 28 10 4 rows selected Name Null Type ——————————— ——————— ———————————— EMPLOYEE_ID NUMBER FIRST_NAME VARCHAR2(30) LAST_NAME VARCHAR2(30) HIRE_DATE DATE SALARY NUMBER(9,2) MANAGER NUMBER DEPARTMENT_ID NUMBER 7 rows selected You should use the asterisk wildcard character primarily for ad hoc querying—when you want an answer from the database that you have not already asked for via programmatic code.
Before you write a SELECT statement, you must determine which table or tables contain the information of interest.