Tag：SQL statement
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Time：2021-10-25
Create and delete constraints using SQL statements Constraint type Primary key constraint: the primary key column data is required to be unique and cannot be empty. Unique constraint: the column is required to be unique and can be null, but only one null value can appear. Check constraint: limit the value range and format of […]
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Time：2021-10-8
In mysql, you can use the SQL statement rename table to modify the table name. The basic syntax of the SQL statement rename table to modify the table name is: Rename table < old table name > to < new table name >; Let’s change the test table to test1 table. 1. First, check which […]
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Time：2021-9-15
In ADO, we need to use multiplication in SQL statements, but after adding ‘*’, the execution program will always make errors. This is because ‘*’ coincides with the ‘*’ keyword in SQL, so compilation will make errors. Solution: put the multiplication operation outside the SQL statement, put the result into a variable, and then reference […]
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Time：2021-9-12
–Generate 300 8-bit non repeating pure digital random numbers DECLARE @i INT=0; DECLARE @j INT; DECLARE @qnum INT=300; — Number of generated random numbers SET NOCOUNT ON CREATE TABLE #temp_Table(num INT) WHILE(@i<@qnum) BEGIN SELECT @j = cast( floor(rand()*(99999999-10000000)+10000000) as int) IF(NOT EXISTS(SELECT num FROM #temp_Table WHERE [email protected] )) BEGIN INSERT #temp_Table (num) VALUES (@j) SET […]
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Time：2021-6-20
In SQL statements, we will inevitably use single quotation mark nesting, but direct nesting is certainly not OK. It is also not OK to use backslash as escape character in Java, and single quotation mark is used as escape character in SQL. For example, the following example is an example of a query in a […]
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Time：2021-5-11
1、 Define table variables Copy codeThe code is as follows: DECLARE @T1 table ( UserID int , UserName nvarchar(50), CityName nvarchar(50) ); Insert into @ T1 (user ID, user name, city name) values (1, ‘a’,’shanghai ‘)Insert into @ T1 (user ID, user name, city name) values (2, ‘B’,’Beijing ‘)Insert into @ T1 (user ID, user […]
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Time：2021-4-22
After converting string string to in, you can use parameter code: public string StringToList(string aa) { string bb1 = “(“; if (!string.IsNullOrEmpty(aa.Trim())) { string[] bb = aa.Split(new string[] { “\r\n”, “,”, “;”, “* ” }, StringSplitOptions.RemoveEmptyEntries); for (int i = 0; i < bb.Length; i++) { If (! BB1. Contains (BB [i])) // remove duplicate […]
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Time：2021-4-11
In addition to viewing the definitions of view and stored procedure in SSMS, you can also use the following statements to query directly: Copy codeThe code is as follows: SELECT object_definition(object_id(‘sys.tables’)); go sp_helptext ‘sys.tables’ go select * from sys.system_sql_modules whereobject_id = object_id(‘sys.tables’) For the following object types:·C = check constraint·D = default (constrained or independent)·P […]
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Time：2021-4-6
Select type, – type of clerk sum(virtual_ memory_ reserved_ kb)as vm_ Reserved_ KB, – reserved memory sum(virtual_ memory_ committed_ kb)as vm_ Committed_ KB, – committed memory sum(awe_ allocated_ kb)as awe_ Allocated_ KB, – memory used after awe is turned on sum(shared_ memory_ reserved_ kb)as sm_ Reserved_ KB, – shared reserved memory sum(shared_ memory_ committed_ kb)as […]
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Time：2021-4-2
sys.dm_ io_ pending_ io_ Requests can return the Current IO pending status. For each pending I / O request in SQL server, a corresponding line is returned, followed by sys.dm_ io_ virtual_ file_ With stats, you can see which database IO has problems. select DB_NAME(database_id) as DBNAME, database_id, file_id, io_stall, io_pending_ms_ticks, scheduler_address from sys.dm_io_virtual_file_stats(null,null)i , […]
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Time：2020-11-23
1. / * get the path and name of the trace file*/ SELECT d.VALUE || ‘/’ || LOWER (RTRIM (i.INSTANCE, CHR (0))) || ‘_ora_’ || p.spid || ‘.trc’ trace_file_name FROM (SELECT p.spid FROM v$mystat m, v$session s, v$process p WHERE m.statistic# = 1 AND s.SID = m.SID AND p.addr = s.paddr) p, (SELECT t.INSTANCE FROM […]
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Time：2020-10-22
If you don’t say much, just give me an exampleinsert Copy codeThe code is as follows: String sql=”insert into allorder values(‘” + orderid + “‘,’” + bookid +”‘,’” + amount + “‘,’” + username + “‘)”; int result=stmt.executeUpdate(sql); if(result==1) response.sendRedirect(“index.jsp”); else response.sendRedirect(“detail.jsp”); delete Copy codeThe code is as follows: String condition=”delete from allorder where id=’”+ […]
