Found a total of 10000 related content
jQuery get array of checked checkboxes ids
Article Introduction：// Get the IDs of all selected check boxes and store them in an array
var checkedIds = $('input[type="checkbox"]:checked').map(function() {
return this.id;
}).get();
console.log(checkedIds);
FAQs about jQuery and checkbox IDs (FAQs)
How to select all checkboxes using jQuery?
Use jQuery to select all check boxes, you can use the ":checkbox" selector. This selection
2025-02-26
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360
SQL Multi-Table Join Query 3 Tables
Article Introduction：By joining multiple tables using the JOIN clause, grouping rows together according to common columns or expressions. Determine a common column or expression: Identifies the common column or expression to join the table. Specify the join type: Select INNER JOIN (match rows), LEFT JOIN (including all rows in the left table), RIGHT JOIN (including all rows in the right table), or FULL JOIN (including all rows in the right table). Use JOIN statement: Use JOIN statement to join tables together and match rows based on common columns or expressions.
2025-04-09
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960
How to select every other table row with CSS Selectors?
Article Introduction：Use tr:nth-child(odd) and tr:nth-child(even) to achieve table interlaced color discoloration. 1.tr:nth-child(odd) select all odd rows, 2.tr:nth-child(even) select all even rows, 3. If the table structure is complex (such as including or merging cells), it is recommended to limit the scope of action such as tbodytr:nth-child(odd) or use JavaScript to dynamically add class name control styles, 4. Manually adding class="alt" to the row and defining background color through .alt is also a stable alternative, but additional HTML logic is required.
2025-06-29
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866
What is the difference between INNER JOIN and LEFT JOIN in MySQL?
Article Introduction：INNERJOIN returns only matching rows in the two tables, while LEFTJOIN returns all rows in the left table, even if there is no match for the right table. For example, when using INNERJOIN to connect users and orders tables, only users with orders are included; while LEFTJOIN contains all users, and the order field for users who have not placed orders is NULL. When selecting JOIN type, you need to pay attention to: use LEFTJOIN and filter NULL values ??when searching for unmatched records; avoid duplicate data selection INNERJOIN; pay attention to the data bloating that the aggregate function may cause; always check the ON condition to ensure correct association. Understanding how both handle non-matching rows is the key to using correctly.
2025-06-17
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762
How do I use Sublime Text's column selection mode?
Article Introduction：SublimeText's column selection mode quickly selects rectangular areas through keyboard and mouse combinations to achieve simultaneous editing of multiple rows. Specific methods include: 1. Drag the Alt mouse on Windows/Linux, and drag the Option mouse on macOS; 2. Select the exact box to use Shift Alt (Windows/Linux) or Shift Option (macOS) to add mouse clicks; 3. Keyboard shortcut Ctrl Alt up/down arrow (Windows/Linux) or Cmd Option up/down arrow (macOS) to add vertical cursor to simulate column selection effect. After entering this mode, the input, deletion, copy and paste operations are all used for all selections.
2025-07-19
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528
mysql full outer join workaround
Article Introduction：MySQL does not support FULLOUTERJOIN, but it can be implemented through LEFTJOIN and RIGHTJOIN combined with UNION. 1. Use LEFTJOIN to obtain all records on the left table and the matching part of the right table; 2. Use RIGHTJOIN to obtain all records on the right table and the matching part of the left table; 3. Combine the results through UNION, pay attention to the possibility of duplicate data. If you need to keep duplicate rows, you can use UNIONALL and manually deduplicate them; 4. Use COALESCE function to unify the source of the primary key to help identify the attribution of records; 5. Pay attention to performance issues, avoid SELECT*, select only necessary fields, and keep the number, type and order of fields consistent to ensure query efficiency and logical correctness.
2025-07-17
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124
How to use the :nth-child() pseudo-class?
Article Introduction：:nth-child() pseudo-class is used in CSS to accurately select specific child elements based on element position. Its basic syntax is element:nth-child(n), which can select the nth child element, and supports odd, even and an b formulas, such as 2n 1 or n 3, respectively, to realize odd line selection or custom interval and starting point. For example, tr:nth-child(even) adds background color to even rows of the table. Unlike :nth-of-type(), :nth-child() calculates all child elements, while the former only calculates the same element. Common uses include zebra pattern tables, gallery layouts, navigation menus and form typesettings. When using them, you need to use them flexibly in combination with specific HTML structures.
2025-06-22
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238
What is a covering index?
Article Introduction：Overwrite index is a database index that contains all columns required for a query, which can significantly improve query performance. 1. Overwrite the index by allowing the database to directly obtain data from the index without accessing table rows, thereby reducing I/O operations and speeding up query speed; 2. It is suitable for frequently executed queries, queries that only select a small number of columns, queries with WHERE conditions, and reports or dashboards that need to be read quickly; 3. When creating, you must include all columns involved in the SELECT, JOIN and WHERE clauses in the index, such as CREATEINDEXidx_coveringONusers(status, name, email); 4. But it is not always the best choice, when queries are frequently changed, table updates are frequently used, and tables are not always the best choice.
2025-06-17
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425
how to group rows in excel for outlining
Article Introduction：In Excel, you can organize multiple rows of data and improve structural clarity through the "grouping" function. The specific operations are as follows: 1. Manually select multiple rows and click the "Combination" button in the "Data" tab to create a group. The numbers will be displayed on the left for expanding/collapse details; 2. After canceling a single group, click "Cancel Grouping" after selecting the area. To clear all groups, click "Clear hierarchical display" after selecting the table; 3. Use Shift Alt RightArrow to create a group, Shift Alt LeftArrow to cancel grouping, Alt A H U to cancel grouping, Alt A H C to clear all groups and other shortcut keys to improve efficiency. Rational use of grouping functions helps to view and maintain layers more efficiently
2025-07-04
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517
Techniques for Constructing Advanced MySQL Queries
Article Introduction：1. The rational use of subqueries and temporary tables can improve the readability and efficiency of query, such as calculating the average score through subqueries and filtering the results; 2. Flexible use of JOIN types such as LEFTJOIN to ensure that all records in the left table are retained; 3. Window functions such as RANK() are used to achieve salary ranking within the department; 4. Clearly specify the return field and use LIMIT to control the number of rows to save resources. To construct advanced MySQL queries, you need to understand the data structure and optimization logic, and combine subqueries, JOIN selection, window functions and field control to ensure accuracy and performance.
2025-07-04
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711
How to debug a slow SQL query?
Article Introduction：The key to slowing SQL queries is to locate the jam points and optimize them in a targeted manner. 1. Check the execution plan, pay attention to whether the Type field is ALL (full table scan), whether the Extra column has Usingfilesort or Usingtemporary, and whether the rows estimate is too large. 2. Check the index usage, including querying whether the field has indexes, whether the index is invalid due to functions or expressions, whether the compound index order is reasonable, and avoid excessive indexing affecting write performance. 3. Reduce unnecessary data processing, avoid complex logic, reduce CASEWHEN and subquery nesting in SELECT, only take necessary fields, and use paging and caching reasonably. 4. Analyze the server and database status to see if there is a lock
2025-07-17
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788
How to use the count tool in Photoshop
Article Introduction：Counting tools are not only used in Photoshop for points, but also record, mark and count specific locations in images. It is hidden in the straw tool group. Right-click the straw tool (shortcut key I) to select the counting tool. After selection, the mouse becomes a small cross with numbers, and a number mark will be added for each click of the image area. The marker appears by default as small red dots and numbers, and you can change the color through the top option bar or switch to the Count Highlight Tool. All markers are saved in the current document and must be saved before closing. View count results to open the Count Panel in the right panel, displaying the total number and supporting storage status. Export recommendations are recommended to save as PSD or PDF to keep the mark. If you need a data table, you can use screenshots or manual records. Other details include
2025-07-11
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872
Dave The Diver: How To Catch Spider Crabs
Article Introduction：In Dave The Diver, there are some creatures that are not easy to catch. Or, catch alive that is. The spider crab is one of those very species, making it seem like the only way to bring these crustaceans back up to land is to viciously crack them up w
2025-01-10
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824
Prepare for Interview Like a Pro with Interview Questions CLI
Article Introduction：Prepare for Interview Like a Pro with Interview Questions CLI
What is the Interview Questions CLI?
The Interview Questions CLI is a command-line tool designed for JavaScript learners and developers who want to enhance their interview
2025-01-10
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1447
Soft Deletes in Databases: To Use or Not to Use?
Article Introduction：Soft Deletes: A Question of DesignThe topic of soft deletes, a mechanism that "flags" records as deleted instead of physically removing them, has...
2025-01-10
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1057
