Summary of the essence of SQL common operations
Table structure and data operations
Copy the table structure：
SELECT * INTO b FROM a WHERE 1<>1 (SQL Serverdedicated) SELECT TOP 0 * INTO b FROM a (More general)
Copy table data：
INSERT INTO b(a,b,c) SELECT d,e,f FROM a
Cross-database copy：
Specify the source database using absolute path
Advanced query skills
Subquery：
Conditional filtering using IN clause
External connection query：
LEFT OUTER JOIN connection method
View query：
Secondary filtering from subquery results
Range query：
BETWEEN contains boundary values, NOT BETWEEN does not contain
Multi-table joint search：
Supports complex association queries of four tables and above
Data Management
Delete orphaned data from the main table：
Use NOT EXISTS to determine the relationship
Random record acquisition：
SELECT TOP 10 * FROM table ORDER BY NEWID()
Delete duplicate records：
Three methods: NOT IN grouping retains the maximum ID, temporary table method, and adds self-increment column method
Practical Tips
Database pagination：
Efficient paging using nested queries and TOP
Grouping maximum value：
Can be used in rankings and other scenarios
Exclude query：
Exclude data from multiple tables using EXCEPT
Metadata query：
Get all table names and column names of the database
Conditional aggregation：
Implement multiple condition statistics using CASE
Table initialization：
TRUNCATE TABLE Quickly clear table
Range selection：
Nested TOP implements the acquisition of specified range records
These SQL operations cover the most commonly used technical points in database development, including table operations, data query, data management, etc., and are the core skills necessary for database developers.
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