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- What are the basic database operation statements?
- The basic operation statements of the database are: 1. To query the database, the statement is [SHOW DATABASES]; 2. To query the structure of the database, the statement is [CREATEDATABASE score]; 3. To create a database, the statement is [DATABASE score DEFAULT CHARSET].
- SQL 14043 2020-06-15 14:05:11
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- What is the difference between hql and sql
- The difference between hql and sql is: 1. The query is different, sql is oriented to database table query, hql is oriented to object query; 2. The judgment conditions are different, the class name followed by from in hql and the class object where are used as conditions for the object's attributes, sql What is followed by from is the table where and then the fields in the table are used to perform conditional queries.
- SQL 16133 2020-06-15 13:19:19
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- Detailed explanation of usage of sql statement case when
- The usage of [case when] in SQL is: 1. Use [case field name when field value then value 1 else value 2 end] to judge the field value; 2. Use [case when condition then value 1 else value 2 end] to judge Field value.
- SQL 53584 2020-06-13 15:08:27
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- MySQL modifies the table structure and its functions of adding, deleting and modifying fields
- mysql is powerful, has many uses, and has many unique uses. This article introduces in detail the MySQL table structure modification and its functions of adding, deleting, and modifying fields. I hope it will help everyone.
- SQL 3980 2020-06-12 09:00:38
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- What is the usage of SQL Union?
- Union is a SQL operator used to combine the results of multiple SELECT statements into a result set. Its syntax is "UNION ALL SELECT * FROM TableB UNION SELECT * FROM TableC".
- SQL 10030 2020-06-09 16:21:31
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- How to use like in sql
- In SQL, like uses wildcards to compare a value with similar values. Its usage is: 1. Percent wildcard character, the syntax is [WHERE SALARY LIKE '200%']; 2. Percent wildcard character, the syntax is [WHERE SALARY] LIKE '_2%3'].
- SQL 20969 2020-06-09 15:40:32
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- What is the sql statement to view the table structure?
- The sql statement to view the table structure is: 1. In mysql, use the sql statement [desc table name] to view; 2. In Oracle, use the sql statement [select * from user_tab_columns where table_name=‘uppercase table name‘] to view.
- SQL 26535 2020-06-08 11:46:50
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- How to delete data using delete statement
- How to use the delete statement to delete data: first create a temporary table; then use the statement "select * from" to query the temporary table; finally use the delete statement "delete #tblDelete where Code = 'Code3'" to delete the data.
- SQL 16636 2020-05-26 10:49:07
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- What are the command phrases used for grouping in database queries?
- The command phrase that needs to be grouped in database queries is "GROUP BY". The "GROUP BY" phrase is used to group the query results and can be used for group summary. The "HAVING" phrase cannot be separated from the "GROUP BY" phrase. exist independently.
- SQL 6844 2020-05-16 09:45:29
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- What is the sql statement to delete an index?
- The SQL statement to delete the index is: [drop index [indexname] on mytable;]. We can use the [alter table tbl_name add index index_name (column_list):] statement to add an index.
- SQL 10424 2020-05-13 11:17:13
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- How to install PLSQl program
- How to install the PLSQl program: first download the "plsql developer" package, unzip it and enter the program directory; then select the "plsql developer" installer and right-click with the mouse; then in the installation interface, select "Agree to the installation agreement"; finally select Just install the path.
- SQL 3533 2020-05-12 10:55:23
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- How to set primary key in database
- How to set the primary key of the database: first open the [SQL Server Management Studio] management tool and connect to the database; then right-click the [Table] menu and select [New] -> [Table]; finally hold down the [ctrl] key and right-click Select [Set Primary Key].
- SQL 27078 2020-05-12 10:45:18
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- What to do if the installation of sql server 2008 fails to restart the computer
- The solution to "Failed to restart the computer" when installing SQL Server 2008: First press the key combination "Win+R" on the keyboard to bring up the run window; then open the registry management interface; finally find and delete " PendingFileRenameOperations" item is enough.
- SQL 7708 2020-05-10 09:02:01
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- What is the usage of exists in oracle?
- Usage of exists in oracle: exists is followed by a subquery, the purpose is to check whether the result of the subquery is true. If the subquery is true, the outer sql statement is executed. exists does not return data, only true or false.
- SQL 8135 2020-05-09 13:17:15
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- What is the full Chinese name of sql?
- The full Chinese name of sql is Structured Query Language. It is a special-purpose programming language, a database query and programming language, used to access data and query, update and manage relational database systems.
- SQL 21095 2020-05-09 10:44:15
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