current location：Home > Technical Articles > Database > Oracle
- Direction：
- All web3.0 Backend Development Web Front-end Database Operation and Maintenance Development Tools PHP Framework Daily Programming WeChat Applet Common Problem Other Tech CMS Tutorial Java System Tutorial Computer Tutorials Hardware Tutorial Mobile Tutorial Software Tutorial Mobile Game Tutorial
- Classify：
-
- What symbols are used to connect strings to the database in Oracle?
- Oracle uses the "||" symbol to concatenate strings. The usage method is as follows: connect the strings to be connected with the "||" symbol; the priority of string connection is low, and parentheses need to be used to ensure the priority; an empty string will still be an empty string after connection; NULL value connection is still NULL.
- Oracle 1042 2024-05-08 19:36:17
-
- How to use with in oracle
- The WITH clause creates temporary tables or views in Oracle. It is used to create complex temporary tables or views, rename query results and improve query performance: Create temporary tables: WITH clause_name AS (subquery) Rename query results: WITH clause_name AS ( subquery) to improve query performance: storing subqueries in temporary tables improves performance
- Oracle 834 2024-05-08 19:33:16
-
- What type is rowid in oracle?
- A ROWID is a proprietary data type in Oracle that uniquely identifies a row in a physical database because it is unique and persistent and persists when the row is moved or updated. Advantages include fast retrieval, can be obtained using the ROWID pseudo-column, and can be used to quickly find, compare, and move rows.
- Oracle 1103 2024-05-08 19:27:17
-
- How to replace string in oracle
- The method of replacing strings in Oracle is to use the REPLACE function. The syntax of this function is: REPLACE(string, search_string, replace_string). Usage steps: 1. Identify the substring to be replaced; 2. Determine the new string to replace the substring; 3. Use the REPLACE function to replace. Advanced usage includes: multiple replacements, case sensitivity, special character replacement, etc.
- Oracle 568 2024-05-08 19:24:20
-
- How to convert string to number in oracle
- Oracle provides multiple methods to convert strings to numbers: TO_NUMBER function: Converts strings to numeric types using the specified format model. NUMTOSTR function: Converts a string to a numeric type and back to a string. VAL function: directly converts a string to a numeric type without checking the format.
- Oracle 573 2024-05-08 19:21:18
-
- Tonumber usage in oracle
- The TO_NUMBER function in Oracle converts a string into a numeric value. It takes a string argument, with the optional format_mask specifying the number format in the string. It returns a value of type NUMBER, or NULL if the conversion fails.
- Oracle 619 2024-05-08 19:18:17
-
- What is used to express a certain character contained in Oracle?
- The representation method of containing a certain character in Oracle is: using the wildcard character %, which means matching any number of any characters. Usage: SELECT * FROM table_name WHERE column_name LIKE '%character%'. In addition, Oracle also provides other wildcards: _ matches a single character; [] matches a single character within square brackets; [^] matches a single character outside square brackets.
- Oracle 483 2024-05-08 19:15:31
-
- What function is used to define a certain character in Oracle?
- INSTR function is used in Oracle to check if a string contains a specific character. Syntax: INSTR(string, substring, [start_position], [occurrence]). It returns the index position of the first occurrence of the substring in the string, or 0 if no match is found.
- Oracle 452 2024-05-08 19:12:17
-
- What function is used to represent a certain character in Oracle?
- In Oracle, you can use the INSTR function to determine whether a string contains a certain character. For example, to find the presence of the character "r" in the string "Oracle", you would use INSTR('Oracle', 'r'). The function returns the index position of the first occurrence of the character if found, or 0 if not found.
- Oracle 1128 2024-05-08 19:06:20
-
- What is the difference between stored procedures and functions in oracle
- The main difference between stored procedures and functions in Oracle: stored procedures have no explicit return type, while functions return an explicit type value. Stored procedures must handle exceptions explicitly, whereas exceptions in functions can be propagated to the caller. Stored procedures are typically executed as part of a transaction, whereas functions are not transactional. A stored procedure must contain a PL/SQL block, while a function can contain a PL/SQL block or just an expression.
- Oracle 816 2024-05-08 19:03:19
-
- How to determine whether two strings are contained in oracle
- In Oracle, you can use the nested INSTR function to determine whether a string contains two substrings at the same time: when INSTR(string1, string2a) is greater than 0 and INSTR(string1, string2b) is greater than 0, it is included; otherwise, it is not included.
- Oracle 895 2024-05-08 19:00:25
-
- What does (+) mean in oracle
- The (+) symbol in Oracle represents the outer join symbol, which is used to join tables and return a result set containing all participating table rows, allowing you to retrieve records in the foreign key table even if no matching record exists in the primary key table. There are three types of outer joins: left outer join, right outer join and full outer join.
- Oracle 1090 2024-05-08 18:57:16
-
- The difference between not equal to null and is not null in oracle
- NOT NULL is a column constraint that prohibits the insertion of NULL values; IS NOT NULL is a check operator that evaluates whether the column does not contain NULL values.
- Oracle 1273 2024-05-08 18:54:17
-
- Why does Oracle filter out null if it is not equal to 1?
- In Oracle, not equal to 1 queries filter out Null values because: Null values are not equal to any value, including 1. Oracle uses three-valued logic to handle Null values, namely true, false, and unknown. A comparison of Null to non-Null values always returns Unknown unless the comparison is Null to Null (which returns True). Queries that are not equal to 1 treat Null values as unknown and filter them out based on Oracle's Null handling mechanism.
- Oracle 1288 2024-05-08 18:51:16
-
- How to write not equal to a certain value in Oracle
- The syntax in Oracle to indicate that it is not equal to a certain value is "column_name <> value". For example, if you want to query employees whose salary is not equal to $1,000, you can use the "SELECT emp_id, salary FROM employees WHERE salary <> 1000;" query.
- Oracle 474 2024-05-08 18:48:15
Recommended Articles
Tool Recommendations
jQuery enterprise message form contact code
jQuery enterprise message form contact code is a simple and practical enterprise message form and contact us introduction page code.
form button
2024-02-29
HTML5 MP3 music box playback effects
HTML5 MP3 music box playback special effect is an mp3 music player based on HTML5 css3 to create cute music box emoticons and click the switch button.
Player special effects
2024-02-29
HTML5 cool particle animation navigation menu special effects
HTML5 cool particle animation navigation menu special effect is a special effect that changes color when the navigation menu is hovered by the mouse.
Menu navigation
2024-02-29
jQuery visual form drag and drop editing code
jQuery visual form drag and drop editing code is a visual form based on jQuery and bootstrap framework.
form button
2024-02-29
Organic fruit and vegetable supplier web template Bootstrap5
An organic fruit and vegetable supplier web template-Bootstrap5
Bootstrap template
2023-02-03
Bootstrap3 multifunctional data information background management responsive web page template-Novus
Bootstrap3 multifunctional data information background management responsive web page template-Novus
backend template
2023-02-02
Real estate resource service platform web page template Bootstrap5
Real estate resource service platform web page template Bootstrap5
Bootstrap template
2023-02-02
Simple resume information web template Bootstrap4
Simple resume information web template Bootstrap4
Bootstrap template
2023-02-02
Cute summer elements vector material (EPS PNG)
This is a cute summer element vector material, including the sun, sun hat, coconut tree, bikini, airplane, watermelon, ice cream, ice cream, cold drink, swimming ring, flip-flops, pineapple, conch, shell, starfish, crab, Lemons, sunscreen, sunglasses, etc., the materials are provided in EPS and PNG formats, including JPG previews.
PNG material
2024-05-09
Four red 2023 graduation badges vector material (AI EPS PNG)
This is a red 2023 graduation badge vector material, four in total, available in AI, EPS and PNG formats, including JPG preview.
PNG material
2024-02-29
Singing bird and cart filled with flowers design spring banner vector material (AI EPS)
This is a spring banner vector material designed with singing birds and a cart full of flowers. It is available in AI and EPS formats, including JPG preview.
banner picture
2024-02-29
Golden graduation cap vector material (EPS PNG)
This is a golden graduation cap vector material, available in EPS and PNG formats, including JPG preview.
PNG material
2024-02-27
Home Decor Cleaning and Repair Service Company Website Template
Home Decoration Cleaning and Maintenance Service Company Website Template is a website template download suitable for promotional websites that provide home decoration, cleaning, maintenance and other service organizations. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-05-09
Fresh color personal resume guide page template
Fresh color matching personal job application resume guide page template is a personal job search resume work display guide page web template download suitable for fresh color matching style. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-02-29
Designer Creative Job Resume Web Template
Designer Creative Job Resume Web Template is a downloadable web template for personal job resume display suitable for various designer positions. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-02-28
Modern engineering construction company website template
The modern engineering and construction company website template is a downloadable website template suitable for promotion of the engineering and construction service industry. Tip: This template calls the Google font library, and the page may open slowly.
Front-end template
2024-02-28
