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- How to modify table name in oracle
- How to modify the table name in Oracle: 1. Use alter table oldname rename to newname to modify the table name; 2. Use rename oldname to newname. This method can only modify tables under your own schema, etc.
- SQL 6992 2020-03-02 15:37:18
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- How to delete table data in oracle
- How to delete table data in Oracle: 1. Use "truncate table table name" to delete all data in the table, which is fast, but cannot be deleted according to conditions; 2. Use "delete from table name where condition" to delete table data, which can be deleted according to conditions. , but slow.
- SQL 21264 2020-02-29 11:58:25
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- How to modify field length in oracle
- How Oracle modifies the field length: Use the modify keyword to modify the field length. The format is: "alter table table name modify field name data type (length)".
- SQL 38561 2020-02-29 11:33:25
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- Oracle deletes duplicate data and keeps the first record
- How Oracle deletes duplicate data and retains the first record: Delete redundant duplicate records in the table. Duplicate records are judged based on a single field ID, leaving only the record with the smallest rowid. Specifically, DELETE, IN, GROUP BY, and NOT are used. , COUNT and other statements.
- SQL 8552 2020-02-29 10:37:46
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- Usage of Case When in SQL
- In SQL, the "Case When" statement is used for selection judgment. During execution, the condition is first judged, and then the corresponding operation is made based on the judgment result; the syntax "CASE field WHEN condition 1 THEN operation 1 WHEN condition 2 THEN operation 2. ..ELSE operation n END;".
- SQL 182633 2022-03-29 16:19:14
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- What to do if sql fails to connect to the server
- SQL connection to the server failed because the database engine did not start. The solution: first click "Start->Programs->Microsoft SQL Server 2008->SQL Server 2008 Peripheral Application Configurator"; then click "Service" and select Start. Can.
- SQL 17176 2020-02-18 10:56:52
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- what is microsoft sql server
- Microsoft SQL Server is a comprehensive database platform that provides enterprise-level data management using integrated business intelligence tools; the Microsoft SQL Server database engine provides more secure and reliable storage functions for relational data and structured data.
- SQL 7820 2020-02-18 10:20:31
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- Usage of inner join in sql
- INNER JOIN is a multi-table connection keyword in SQL. The syntax is: SELECT * FROM table1 INNER JOIN table2 ON table1.field1 compopr table2.field2, which is used to query related data between two tables.
- SQL 12025 2020-02-14 16:22:45
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- What does where 1=1 mean in SQL statement?
- Where 1=1 in the SQL statement is automatically generated by the program to avoid grammatical errors caused by the first word after the where keyword being "and".
- SQL 7853 2020-02-13 17:19:58
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- The principle of SQL injection attack
- The principle of SQL injection attack: A malicious user inserts a SQL statement into the request content during the process of submitting a query request. At the same time, the program itself overly trusts the user input content and fails to filter the SQL statement inserted by the malicious user, causing the SQL statement to be directly Server-side execution.
- SQL 16391 2020-02-13 17:13:33
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- What is the SQL statement to create a view?
- SQL creates a view using the create view statement. The specific usage is as follows: create view viewname as select * from <name of table> where <some restrictions>.
- SQL 33347 2020-02-13 16:56:09
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- Usage of case when in sql
- Case has two formats: simple case function and case search function. The simple case function is relatively simple to write, but compared with the case search function, there are some functional limitations, such as writing predicates.
- SQL 22483 2020-02-13 16:35:04
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- What does 'select 1 from table' mean?
- "Select 1 from table" means to check whether there are records in the table. 1 is a constant, and the value of all rows found is it. In terms of efficiency, 1>column>*, because 1 does not need to look up the dictionary table .
- SQL 20700 2020-02-13 16:13:14
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- How to delete data using sql statement
- SQL can use the delete statement to delete data. The syntax is "delete from table name where...". When where does not match any records, no data will be deleted. When the where statement is not written, the table will be deleted. All data.
- SQL 42265 2020-02-07 13:16:18
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- sql intercepts the first digits of a string
- In SQL, you can use the LEFT function to get the first few digits of a string. The syntax is "LEFT(string,length)", string is the intercepted string, and length is the length to be intercepted, for example, LEFT("www.php. cn",3) can intercept www.
- SQL 23920 2020-02-07 12:37:29
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