Showing posts with the label SQL

Five top SQL Query Performance Tuning Tips

SQL query runs faster when you write it in a specific method. You can say it as tuning. There are five tuning tips: List of Performance Tuning Tips use index columns, use group by, avoid duplicate column in SELECT & Where, use Left Joins use a co-related subquery. Five top SQL Query Performance Tuning Tips SQL Performance Tuning Tip: 01 Use  indexes in the where clause of SQL . Let me elaborate more on that. Be sure the columns that you are using in the WHERE clause should be already part of the Index columns of that database Table. An example SQL Query: SELECT *  FROM emp_sal_nonppi WHERE dob <= 2017-08-01; SQL Performance Tuning Tip: 02 Use GROUP BY . Some people use a  DISTINCT clause to eliminate duplicates . You can achieve this by GROUP BY. An example SQL Query: SELECT E.empno, E.lastname FROM emp E,emp_projact EP WHERE E.empno = EP.empno GROUP BY E.empno, E.lastname; SQL Performance Tuning Tip: 03 Avoid using duplicates in the Query. Some people use the same col

SQL: 8 Frequently Used DATE Functions

SQL DATE function for all Developers. DATE Function is powerful in SQL. In SQL projects, people use this Function variety of ways. All projects depends in DATE, and without it there is no way of existing of project.  The Quick tour helps you use this function effectively.  You can learn Oracle SQL step by step for all Developers. Below is the list of SQL DATE functions SYSDATE - It returns current local DATE and Time CURRENT_DATE - Return local DATE and TIME and adjusted to current session Time Zone. ROUND (DATE) - Rounds to nearest DAY TRUNC (DATE) - Truncates Time MONTHS_BETWEEN(date1,date2) - Returns number of months between date1 and date2' LAST_DAY(DATE)- Returns last of the month ADD_MONTHS(date,integer_months) - Adds specified number of months to specified date. NEXT_DAY(date, day_of_week) - Returns to next day of the week that comes after the specified DATE Also Read   The Best SQL Book for all Developers.

3 SQL Query Examples to Create Views Quickly

There are three kinds of Views in SQL. The three views are Read-only, Force, and Updatable. Views real usage is to hide data. And you need to ensure base tables are present before you create a View. You can call views as logical tables. The advantage of Views is you can show only some of the fields of base tables. What is a View in SQL A view can be constructed with another view so it is called a nested view. You can create or replace an existing view A view can be created without having base tables. This is possible with the FORCE option. #1: Read-Only Views The standard syntax for the view is as follows: CREATE OR replace VIEW invoice_summary AS SELECT vendor_name count(*) AS invoice_count, SUM(invoice_total) AS invoice_total_sum FROM vendor JOIN invoices ON vendors.vendor_id*invoices.vendor_id GROUP BY vendor_name; Notes: You cannot update Read-only Views #2: Force Views CREATE FORCE VIEW products_list AS SELECT product_description, product_price FROM products;

PL/SQL Sample code and error handling mechanism

SAMPLE PL/SQL CREATE TABLE dummy ( dummy_value VARCHAR2(1)); DECLARE -- Define local variable. my_string VARCHAR2(1) := ' '; my_number NUMBER; BEGIN -- Select a white space into a local variable. SELECT ' ' INTO my_string FROM dummy; -- Attempt to assign a single white space to a number. my_number := TO_NUMBER(my_string); EXCEPTION WHEN no_data_found THEN dbms_output.put_line('SELECT-INTO'||CHR(10)||SQLERRM); END; / Output and Error: The program returns the following output, which illustrates formatting user- defined exceptions.  The CHR(10) inserts a line return and provides a clean break between the program's SQLCODE and SQLERRM messages: RAISE my_error SQLCODE [1]  SQLERRM [User-Defined Exception]