Oracle SQL

Oracle SQL

Oracle SQL is a database management system that is widely used around the world. It’s best suited for commercial and enterprise applications and is especially popular in large corporations with mission-critical databases. Mastering Oracle SQL will thus undoubtedly lead to exciting chances. Oracle SQL incorporates various modifications to the ANSI/ISO standard SQL language and additional commands provided by Oracle tools and applications. SQL*Plus and Server Manager from Oracle allows you to run any ANSI/ISO standard SQL statement on an Oracle database, as well as additional commands or functions.

Although some Oracle tools and applications reduce or hide the use of SQL, SQL is used for all database operations. Any other means of data access would evade Oracle’s security and potentially jeopardize data security and integrity.

Free Oracle SQL Practice Test Online

The relational database management system is Oracle SQL. It is common in enterprise applications. A database is a collection of structured data that is stored electronically. The database stores the data and provides access, management, and assistance locating essential information. Relational database management (RDBMS) has grown in popularity and efficiency over the previous flat-file paradigm, and RDBMS allows you to eliminate unnecessary data. Oracle SQL is the most well-known relational database technology, accounting for a sizable portion of the market among other relational databases. The following are the important Oracle SQL features:

  • Unleash the full scope of query: SQL Analytic
  • Conformance with standards: ANSI SQL compliance

  • Indexes, in-memory, partitioning, and optimization all contribute to performance.

  • Read consistency across multiple versions

  • Text and spatial

  • PL/SQL and Java are two procedural extensions.

Oracle SQL Normalization

Normalization is a set of actions to create a database design that enables efficient data access and storage. These methods limit data redundancy and the likelihood of data inconsistency. Normalization also aids in the organization of data in a database. It is a multi-step procedure that converts data into a tabular format and removes duplicate data from relational tables. Normalization organizes a database’s columns and tables to guarantee that database integrity constraints execute their dependencies correctly. It is a method of deconstructing tables used to minimize data redundancy (repetition) and undesired characteristics such as Insertion, Update, and Deletion anomalies. It becomes difficult to manage and update the database without data loss if it is not normalized.

  • First Normal Form – Avoids repeated groups by placing them on their table and connecting them with a one-to-many relationship.
  • Second Normal Form – Every non-key property must be dependent on the entirety of every candidate key, not simply a portion of a key.
  • Third Normal Form – Non-key attributes must only be dependent on candidate keys.
  • Fourth Normal Form – Divides independent multi-valued data recorded in a single table into different tables.
  • Fifth Normal Form – Distinguishes data redundancy that is not addressed by any of the other normal forms.

Oracle Live SQL

Oracle Live SQL is a new Oracle Database 12c that enables developers to design and run SQL scripts against Oracle databases easily. It is appropriate for fast code demonstrations, debugging, and troubleshooting. In general, it is a more convenient manner for people teaching or presenting SQL, PL/SQL, or another Oracle function to use Oracle. The advantage of Oracle Live SQL is that it works with any database on the platform (not just Oracle), so you have an option. It allows you to see the query’s execution strategy in real-time without waiting for it to complete. You can also see if your indexes are being used correctly and which ones require updating.

Furthermore, Oracle Live SQL supports more complex queries, such as text searches using RegExp or wildcards (*). This new technology enables you to change your live data while querying it. This implies that any changes you make will automatically be reflected in the database.

DATE DIFF in Oracle SQL

The DATEDIFF function calculates the difference between two dates in various units. To determine the difference in days or seconds between two dates or datetimes, use the @DATEDIFF function. The DATEDIFF function receives three parameters: the first is a datepart (which might be a year, quarter, month, day, hour, etc.) and the remaining two dates to compare. The SQL DATEDIFF function returns the number of specified datepart boundaries crossed between the supplied startdate and enddate.

Syntax:

@DATEDIFF (‘difference’, ‘date’, ‘date’)

Cursor Loop Oracle SQL

The cursor FOR LOOP statement opens a cursor and implicitly declares its loop index as a record variable of the row type that a given cursor returns. With each iteration, the cursor FOR LOOP command fetches a row from the result set into the record. The cursor FOR LOOP statement closes the cursor when there are no more rows to fetch. If a statement inside the loop transfers control outside the loop or produces an exception, the cursor also closes.

When all of the records in the cursor have been obtained, the CURSOR FOR LOOP will end. When you wish to fetch and process every entry in a cursor, you will use a CURSOR FOR LOOP.

Syntax:

FOR record_index in cursor_name

LOOP

   {…statements…}

END LOOP;

Parameters:

  • record_index – This is the record’s index.
  • cursor_name – The name of the cursor from which you want to get records.
  • statements – The code instructions to be executed go via the CURSOR FOR LOOP.
Oracle SQL Certification

Oracle SQL Email Validation

Email validation in SQL can be accomplished in a variety of ways. The best technique to validate an email is to utilize regular expressions. Before Oracle 11G, the developer must construct a SQL function for email validation. Email validation is also possible in SQL servers. SQL Server has a PATINDEX function, similar to the REGEXP function in Oracle. Oracle 11 G is used to write the REGEXP function. Before that, the user must write a function, which must then be used in a procedure or select statement. If the email address is correct, the provided function will return ‘SUCCESS,’ else it will return ‘FAILURE.’

Most Recent Date Oracle SQL

Knowing how to retrieve the current date and time in any language is essential. Until Oracle8i Database, there was only one way to acquire the date and time in PL/SQL: utilize the SYSDATE function. Beginning with Oracle9i Database, you have access to all Table functions, and you must grasp how they work and your options.

 

Function

Time Zone

Datatype Returned

SYSDATE

Database Server

DATE

CURRENT_DATE

Session

DATE

SYSTIMESTAMP

Database Server

TIMESTAMP with TIME ZONE

CURRENT_TIMESTAMP

Session

TIMESTAMP with TIME ZONE

LOCAL TIMESTAMP

Session

TIMESTAMP

Oracle SQL Limit Rows

The optimal strategy for limiting rows in Oracle will consider performance, flexibility, and the database version you are using. If you’re running Oracle 12c, use the FETCH syntax, which was designed specifically for this purpose. If you aren’t using Oracle 12c, we recommend using the AskTom approach, which was advocated by Tom Kyte and is widely utilized by Oracle customers. So that’s how you may build a query in Oracle to limit the number of rows returned.

All database systems do not support the SELECT TOP clause. To pick a limited number of records, MySQL supports the LIMIT clause, whereas Oracle employs FETCH FIRST n ROWS ONLY and ROWNUM. ROWNUM is a query-accessible pseudocolumn (not a real column). The numbers 1, 2, 3, 4,… N will be allocated to ROWNUM, where N is the number of rows in the set ROWNUM is used. A ROWNUM value is not assigned to a row indefinitely (this is a common misconception). A row in a table does not have a number; there is no such thing as row 5 in a table. A ROWNUM value is assigned to a row after it has passed the query’s predicate phase but before it is sorted or aggregated.

Oracle 12 Syntax:

SELECT column_name(s)

FROM table_name

ORDER BY column_name(s)

FETCH FIRST number ROWS ONLY;

 

Older Oracle Syntax:

SELECT column_name(s)

FROM table_name

WHERE ROWNUM <= number;

 

Older Oracle Syntax (with ORDER BY):

SELECT *

FROM (SELECT column_name(s) FROM table_name ORDER BY column_name(s))

WHERE ROWNUM <= number;

Oracle SQL Replace New Line Character

Oracle SQL select statement from a table containing newline characters (such as \n, \r, \t) and replace it with a space ” “.  This is simple to accomplish using ASCII codes and the dreaded TRANSLATE() command. This substitutes space for newline, tab, and carriage return. TRANSLATE() is far more efficient than its regex counterpart.

select translate(your_column, chr(10)||chr(11)||chr(13), ‘    ‘)

from your_table;

The REGEXP_REPLACE function in Oracle/PLSQL is an expansion of the REPLACE function. This method, introduced in Oracle 10g, allows you to use regular expression pattern matching to replace a sequence of characters in a string with another set of characters. Oracle’s REGEXP_REPLACE function syntax is as follows:

REGEXP_REPLACE( string, pattern [, replacement_string [, start_position [, nth_appearance [, match_parameter ] ] ] ] )

Count in Oracle SQL

COUNT is an important Numeric/Math function in Oracle. It is used to calculate the count of an expression. The COUNT function is supported in all Oracle/PLSQL versions, including Oracle 12c, Oracle 11g, Oracle 10g, Oracle 9i, and Oracle 8i. The COUNT() method in Oracle is an aggregate function that returns the number of items in a group.

Syntax: 

COUNT( [ALL | DISTINCT | * ] expression)

  • If you use DISTINCT, you can only specify the query partition clause of the analytic clause. The order by clause and windowing clause clauses are not permitted.
  • COUNT returns the number of rows where expr is not null if you specify it. You can count either all rows or simply distinct expr values.
  • Suppose you provide an asterisk (*); this function will return all rows, including duplicates and nulls. COUNT will never return null.

Oracle SQL Question and Answers

There are several ways to remove decimal values in SQL:

  • Using the ROUND () function: This function in SQL Server is used to round a particular number to a certain number of decimal places.
  • Using the FLOOR () function: Returns the largest integer value less than or equal to a number.
  • Using the CAST () function: Explicit conversion must be performed in SQL Server using the Cast or Convert functions.

To access SQL scripts:
Sign in to the workspace home page.

  •  To display the SQL Scripts page, do one of the following: 
  • Click the SQL Workshop icon and click SQL Scripts to go to the SQL Scripts page.
  • Click the down arrow to the right of the SQL Workshop icon to display a drop-down menu. Then select the SQL Script menu option.

A structured query language (SQL) is a set of statements that all programs and users use to access data in an Oracle database. Application programs and Oracle tools often allow users to access the database without using SQL directly, but these applications must use SQL when executing their requests.

  • From the Oracle SQL Developer menu, go to Tools> Settings.
  • In the left pane of the Settings dialog box, select Database> NLS. 
  • From the list of NLS parameters, enter DD-MON-RR HH24: MI: SS in the Date Format field.
  • Save and close the dialog. That’s it.
  • In SQL Developer, click the Reports tab on the left side of the Connection Navigator. … 
  • In the Report Navigator, expand Data Dictionary Report.
  • Under Data Dictionary, expand Report on Database. 
  • Under About Database, click Version Banner.
  • Start the comment with a slash and an asterisk (/ *). Continue with the comment text. This text can span multiple lines. .. .. 
  • Start the comment with-(two dashes). Continue with the comment text. This text cannot be broken.

This can be easily done using equals to(=), less than(<), and greater than(>) operators.

Use the ALTER TRIGGER statement to recompile a trigger manually.

  •  In the terminal window, set the environment variables. Change to the sqldeveloper directory under $ ORACLE_HOME. Start SQL Developer by running the shsqldeveloper.sh command.
  • In the Connections navigator, right-click the Connections node and select New Connection.
  • Enter the selected connection name, system user name, and password for the SYSTEM user. Select Save Password if you want to save the password for future connections as this user. Accept the default connection type and role. Enter the host name, port, and SID. You can click Test to verify that the connection is working properly. Click Connect. 
  • The connection appears on the Connections tab on the left and the SQL Worksheet opens automatically.

To delete a table: In SQL Developer, follow the steps in View Tables to the PURCHASE_ORDERS table in the HR schema. Right-click the PURCHASE_ORDERS table, select Tables, and then select Delete.

The easiest way to escape single quotes in SQL is to use two single quotes.

Exclude Weekends in Oracle SQL Using to_char(date, `DY’) Function. SELECT * FROM sales_orders WHERE TO_CHAR(order_date, ‘DY’) NOT IN (‘SAT’, ‘SUN’) and trunc(order_date) >= trunc(sysdate) – 30; The statistics output will consist of all days besides Saturdays and Sundays.

In Oracle SQL Developer, click the Tools menu and select the Export Database option. The following window is displayed. Specify Scheme from the Connection drop-down menu and select the check boxes as needed. Also specify the name and location of the export file.

The SQL LIMIT clause limits the number of rows returned by the SELECT statement. For Microsoft databases such as SQL Server and MS Access, you can use the SELECT TOP statement to limit the results. This is equivalent to Microsoft’s own SELECT LIMIT statement.

To execute a query using multiple statements, make sure that each statement is separated by a semicolon. Then set the DSQEC_RUN_MQ global variable to 1 and run the query. If the variable is set to null, all statements after the first semicolon will be ignored.

Open SQL Developer and connect to the Oracle database. Then, in the Connections pane on the left, expand the schema node that runs the stored procedure. Then expand the Procedures node, select the stored procedure you want to run, and right-click.

Right-click within editor to show the pop-up-menu. Select Unwrap or simply press Ctrl-Shift-U to unwrap the code.

Press Control-Shift-L to open the log. This is the message log by default, but when I create the item that is causing the error, I see the compiler log.

Dynamic SQL is a programming technique that allows you to dynamically create SQL statements at run time. The full text of SQL statements can be unknown at compile time, so you can use dynamic SQL to create more versatile and flexible applications.

SQL plan management uses a mechanism called SQL plan baseline. A plan baseline is a set of accepted plans that the optimizer can use for SQL statements. In a typical use case, after verifying that the plan is working properly, the planning baseline in the database simply contains the plan.

SQL_ID is just another hash of the library cache object name. In fact, after 10g, the whole story is as follows. Oracle has MD5 hashed the library cache object name and generated a 128-bit hash value.

The SQL Trace feature and TKPROF are two basic performance diagnostic tools that help you monitor and tune applications running on your Oracle server.

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