Updating a select

01-Apr-2020 18:30 by 9 Comments

Updating a select

The SQL Server (Transact-SQL) UPDATE statement is used to update existing records in a table in a SQL Server database.There are 3 syntaxes for the UPDATE statement depending on whether you are performing a traditional update or updating one table with data from another table.

In Oracle SQL Developer, an easy way to construct a SELECT statement is to drag and drop a table name from the TABLES node in the Connections Navigator into the SQL Worksheet.

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.

You can use WHERE clause with UPDATE query to update selected rows, otherwise all the rows would be updated.

Following is the basic syntax of UPDATE query with WHERE clause.

(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.

The first value is assigned to the first column in the list, the second value is assigned to the second column in the list, and so on. Only rows that meet the search condition are updated.

If you omit this clause, all rows in the table are updated.

The subquery must return exactly one row that includes all the columns listed.

The column values returned by the subquery are assigned to the columns in the column list in order. WHERE search_condition Chooses which rows to update in the database table.

tablespace_name, s.extent_management FROM user_tables t, user_tablespaces s WHERE t.tablespace_name = s.

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