current location：Home > Technical Articles > Database > SQL
- Direction：
- All web3.0 Backend Development Web Front-end Database Operation and Maintenance Development Tools PHP Framework Common Problem Other Tech CMS Tutorial Java System Tutorial Computer Tutorials Hardware Tutorial Mobile Tutorial Software Tutorial Mobile Game Tutorial
- Classify：
-
- How to express decimals in SQL
- In SQL, decimals are typically represented using the DECIMAL or NUMERIC data types. DECIMAL is used to represent decimals with fixed precision and scale, whereas NUMERIC allows variable precision and scale. Choosing the appropriate type depends on the precision and variability of decimals required.
- SQL 652 2024-04-28 11:24:13
-
- The meaning of @ in sql
- The @ symbol in SQL represents a placeholder for a parameter, used to store dynamic or unspecified values. Specific usage scenarios include stored procedures/functions, dynamic SQL, and query parameterization.
- SQL 630 2024-04-28 11:14:32
-
- The meaning of * in sql
- In SQL means all columns, it is used to simply select all columns in a table, the syntax is SELECT FROM table_name;. The advantages of using include simplicity, convenience and dynamic adaptation, but at the same time pay attention to performance, data security and readability. In addition, it can be used to join tables and subqueries.
- SQL 1294 2024-04-28 11:09:16
-
- What does ^ mean in sql
- The ^ symbol in SQL represents the bitwise XOR operation, which compares two binary bits and returns a new bit. The rules are: 0^0=0, 0^1=1, 1^0=1, 1^1=0. Uses include setting or removing flags, comparing values, and simple encryption and decryption.
- SQL 1333 2024-04-28 11:06:14
-
- Usage of * in sql
- * in SQL is a wildcard character with the following usage: Query all columns: SELECT * FROM table_name; Alias all columns: SELECT * AS all_columns FROM table_name; Find specific values in the WHERE clause: SELECT FROM table_name WHERE LIKE '%value %';Use with aggregate functions: SELECT SUM(*) FROM table_name;
- SQL 659 2024-04-28 11:00:24
-
- What does like mean in sql
- The SQL LIKE operator is used for pattern matching, and the syntax is SELECT * FROM table_name WHERE column_name LIKE pattern; The pattern can use wildcard characters % (any character) and _ (single character), and supports escape characters, character ranges, and NOT LIKE negative matching. But be aware that the LIKE operator is case-sensitive and may be slower for large data tables.
- SQL 636 2024-04-28 10:57:14
-
- What does group by mean in sql
- The GROUP BY clause is used to group data and perform aggregation operations based on groups. It groups groups of rows with the same value together and calculates summary values or filtered data within each group.
- SQL 905 2024-04-28 10:54:12
-
- Usage of loop in sql
- LOOP is a control structure in T-SQL that is used to repeatedly execute a block of statements until specific conditions are met. It provides loop control, flexibility, and simplicity, but also requires attention to exit conditions and potential infinite loops.
- SQL 1326 2024-04-28 10:51:13
-
- How to write not equal to 0 in sql
- In SQL, to determine whether a value is not equal to 0, you can use the inequality operator !=, and the syntax is: expression != 0. For example, to find all records that are not equal to 0, you can use SELECT * FROM table_name WHERE column_name != 0;
- SQL 910 2024-04-28 10:48:13
-
- How to express not equal to null in sql
- The representation of not equal to NULL in SQL is: IS NOT NULL. This operator checks whether an expression is not equal to NULL and returns a Boolean value: TRUE if the expression is not equal to NULL; otherwise, FALSE.
- SQL 579 2024-04-28 10:45:21
-
- How to write not equal to a certain condition in sql
- The <> operator is used in SQL to indicate that it is not equal to a certain condition. The example is as follows: SELECT * FROM table_name WHERE column_name <> 'value';
- SQL 790 2024-04-28 10:42:13
-
- Usage of all in sql
- ALL operator is used to combine all rows of multiple query results, as opposed to DISTINCT which only returns unique rows. It is used to return all rows, ignore duplicates, and handle NULL values. The difference with DISTINCT is that ALL returns all rows, including duplicate rows, while DISTINCT returns only unique rows.
- SQL 1100 2024-04-28 10:36:15
-
- Usage of multiple fields in sql
- There are two ways to use the IN operator on multiple fields in SQL: through a subquery or directly listing multiple values. Subqueries are used to retrieve values from other queries, while multiple values can be listed directly separated by commas. The IN operator checks whether a given value is in the list of specified values.
- SQL 1070 2024-04-28 10:33:15
-
- The meaning of in in sql
- The IN operator in SQL is used to check whether a value belongs to a list of specified values. It can: Check multiple values Optimize performance Improve readability
- SQL 932 2024-04-28 10:30:20
-
- What is the command to delete a table in sql
- The command in SQL to drop a table is DROP TABLE. This command deletes a table by specifying the table name. The syntax is as follows: DROP TABLE table_name. To delete a table, please enter the command and execute the command in sequence to ensure that the table is not referenced by other objects. It is recommended to back up the table before deleting.
- SQL 987 2024-04-28 10:21:10
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
