current location：Home > Technical Articles > Database > SQL
- 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 does the percent sign mean in sql
- The percent sign (%) in SQL is a wildcard character that represents any number of characters and is mainly used for string comparison and fuzzy queries: String comparison: used to match character sequences that begin with a specific string. Fuzzy query: Used to match fields in a table that contain a specific sequence of characters, regardless of the remainder of the field. Regular expressions: Can be used with regular expressions in some databases to match strings with specific patterns.
- SQL 624 2024-05-01 23:24:42
-
- Usage of varchar and numeric in sql
- VARCHAR is used to store variable-length strings (1-8000 characters), and NUMERIC is used to store precise numbers (specified length and precision). The difference between the two lies in length, data type, precision, and storage space. The length of VARCHAR is variable, and the length of NUMERIC is fixed; VARCHAR stores strings, and NUMERIC stores numbers; NUMERIC has higher precision; VARCHAR only stores the necessary length, and NUMERIC always occupies the specified length.
- SQL 609 2024-05-01 23:21:51
-
- What does the group by statement in sql mean?
- The GROUP BY statement is used to group data by specified columns or combinations of columns and perform aggregate functions (such as sum, count, average) on each group to summarize the data. The syntax is: SELECT column 1, column 2, ...FROM table name GROUP BY group column
- SQL 1184 2024-05-01 23:21:16
-
- Group by usage in sql
- The GROUP BY statement in SQL groups the data set by specified columns and performs aggregate calculations on each group. Usage is as follows: Identify grouping columns: Specify the columns to be grouped. Aggregation functions: Use SUM, COUNT, AVG and other functions to calculate grouped values. Grouped results: The query returns grouped results, showing the aggregated calculated value of each group.
- SQL 579 2024-05-01 23:18:52
-
- How to use groupby in sql
- The GROUP BY clause groups the data set by the specified column and aggregates the specified value of each group, syntax: SELECT aggregate_function(column_name) FROM table_name GROUP BY column_name. Its usage includes: 1. Aggregating data (calculating the sum, average, etc. of each group); 2. Grouping data (dividing data into groups by specified columns); 3. Filtering data (combined with the HAVING clause).
- SQL 1368 2024-05-01 23:18:36
-
- The role of order by in sql
- The ORDER BY clause in SQL sorts the rows in the result set to display the data in a specific order. It sorts one or more columns in ascending or descending order, and supports advanced usage such as multi-column sorting, null value handling, and more.
- SQL 679 2024-05-01 23:18:17
-
- What does groupby mean in sql
- GROUP BY is a statement in SQL used to group and aggregate data. It groups rows by grouping key and then applies aggregate functions such as calculating sum, count, or average.
- SQL 994 2024-05-01 23:15:52
-
- The meaning of order by in sql
- The ORDER BY clause in SQL is used to sort query results by specified columns. You can specify ascending order (ASC) or descending order (DESC), and you can also specify multiple sorting conditions. By default, NULL values are treated as the maximum value, this behavior can be changed using the IS NULL clause.
- SQL 877 2024-05-01 23:15:24
-
- How to use orderby in sql
- The OrderBy clause is used to sort SQL query results by specified columns. Syntax: SELECT ... ORDER BY column1 [ASC|DESC], column2 [ASC|DESC], ... Parameters: 1. Column to be sorted 2. Optional sort order: [ASC (ascending) | DESC (descending) )]
- SQL 1043 2024-05-01 23:12:52
-
- The role of where in sql
- The WHERE clause is used in SQL to filter rows based on specific criteria, selecting only the rows that meet the criteria. It improves query speed, accuracy, and data integrity.
- SQL 547 2024-05-01 23:12:35
-
- How to use like statement in sql
- The LIKE statement is used to match characters or strings based on a pattern in SQL. The syntax is: SELECT column_name FROM table_name WHERE column_name LIKE 'pattern'. It uses % to match zero or more characters, _ to match a single character, [ ] to match characters within square brackets, and ^ to match any character except the specified character. The default is case-sensitive, you can use the COLLATE clause for case-insensitive matching.
- SQL 712 2024-05-01 23:12:19
-
- The role of round in sql
- The ROUND function is used to round a number to a specified number of decimal places, with the syntax ROUND(number, decimals). Its functions include formatting numbers, calculating based on precision, and creating derived columns with a specified number of decimal places.
- SQL 1255 2024-05-01 23:09:52
-
- How to express not equal to empty in sql
- There are two ways to write not equal to null in SQL: 1. IS NOT NULL; 2. <> ''. Using the IS NOT NULL query will return records where the column is not NULL, while using the <> '' query will return records where the column is not equal to the empty string.
- SQL 1272 2024-05-01 23:09:15
-
- Function that converts multi-row values into one row in sql
- The function in SQL that converts multiple rows of values into one row is ARRAY_TO_STRING(), which converts an array into a comma-separated string. Used in conjunction with aggregate functions such as GROUP_CONCAT(), data from multiple rows can be grouped and converted into a single row.
- SQL 433 2024-05-01 23:06:49
-
- How to write multiple likes in sql
- In SQL, you can use multiple LIKE conditions to match partially matched string values. You can use the following method: Use the OR operator to connect multiple LIKE conditions to match rows that meet any condition. Use the IN operator to specify a list of values, matching a condition where the column value matches an exact value in the list. Use subqueries to create subsets, and then match multiple strings through the main query.
- SQL 1454 2024-05-01 23:06:33
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
