sql-update

问题 I am using EJB and Container managed EM ( for local testing I am creating em here). I have a requirement where I need to update database based on some condition, My issue is Update is taking very long time , how to reduce it ? I tried two approach 1> Update Query 2> Update in entity Please let me know if I am doing any mistake, or any other approach exist. Note : code for update is below public class Test { private static final int OaOnaccount = 0; private static final int ArrayList = 0;

问题 I have a pretty simple mysql record like this: +------+-------+-----------+ | id | name | password | +------+-------+-----------+ | 1 | John | d0c91f13f | +------+-------+-----------+ ... ... ... And here is its hibernate entity; nothing fancy @Entity @Table(name = "user", schema = "", catalog = "trade") public class UserEntity{ private long id; private String name; private String password; @Id @Column(name = "id") public long getId(){ return id; } public void setId(long id){ this.id = id; }

问题 When updating a table in mysql, for example: Table user user_id | user_name 1 John 2 Joseph 3 Juan If I run the query UPDATE `user` SET user_name = 'John' WHERE user_id = 1 Will MYSQL write the same value again or ignore it since it's the same content? This is a Q&A question I made, as Stack Overflow encourages it, I think it will be helpful in the future for the fellow programmers with the same question. 回答1: As the MYSQL Manual for the UPDATE statement implies, If you set a column to the

问题 I always use DataGridView.DataSource = (DataTable)tbl; But this method is completely refresing the Datagridview something like selectedrows, scrollbar position, backColor etc.. I only want to update cell data from SQL witouth full datagridview refresh For Example uTorrent has a table like datagridview, and in some cells x KB/s values always refresing but torrentdatagrid is static. there is No scroll moving, no selection dissapearing etc. Can you help me to do this? I'm sorry for my bad

问题 I am using MERGE statement in order to insert XML input to SQL Server database table. How to execute multiple conditions in WHEN MATCHED block. Please refer the below code. USING TableRelationship AS new ON (new.TableRelationshipTypeID = old.TableRelationshipTypeID) AND old.ToRoleID = @RoleID WHEN MATCHED THEN UPDATE SET old.FromRoleID = new.FromRoleID -- Condition 2 -- Condition 3 Currently WHEN MATCHED it only executes this old.FromRoleID = new.FromRoleID line. How can I execute all 3 lines

问题 I am adding batches of records to a table using a single insert statement. I want each new batch to be allocated incrementing numbers, but starting from 1 each time. So, if I have Batch Name IncementingValue 1 Joe 1 1 Pete 2 1 Andy 3 2 Sue 1 2 Mike 2 2 Steve 3 and I then add two records (using a single insert statement) : 3 Dave 3 Paul How can I run an update statement against this table so that Dave will be set to 1 and Paul to 2. I don't want to use a cursor. 回答1: The ranking function ROW

问题 I have two tables in SQLite which look like this TABLE_X ____________________ | id | C1 | C2 | C3 | C4 | | 10 | 99 | 03 | 04 | 00 | | 60 | 88 | 20 | 30 | 40 | TABLE_Y ___________ | id | C2 | | 10 | 11 | | 60 | 22 | I am trying to write query to update records on Table X based on records in Table Y The condition for the updateis something like the following update table_x set table_x.c1 = 100, table_x.c2 = table_y.c2 where table_x.id = table_y.id But when I try to do this I get an error

问题 I have a select like this: SELECT field1, field2, field3 FROM table WHERE field1= 5 AND field_flag =1 GROUP BY field1, field2, field3 limit 1000; I want to update field_flag for the resulting rows. How can I do that in MySQL? 回答1: Do you mean that you want to update table where field1, field2, and field3 are in the set returned by your select statement ? eg. update table, ( select field1, field2, field3 FROM table WHERE field1= 5 AND field_flag =1 GROUP BY field1, field2, field3 limit 1000 )

问题 Given this table in PostgreSQL 9.6: CREATE TABLE test_table ( id int PRIMARY KEY , test_array text[] ); With a row like: INSERT INTO test_table (id, test_array) VALUES (1 , '{A,A,A,B,B,B}'); How would I remove one single 'B' value? I cannot use: UPDATE test_table SET test_array = array_remove(test_array, 'B') WHERE id = 1; as it removes all elements of value 'B'. I am just looking to remove a single element (say, the first one). Any ideas? 回答1: Based on my old answer on dba.SE that you found

问题 I would like to update the table using case statement the query is like this... select case(@columnname) when 'name1' then begin update table set pay1=pay1* 100 pay2=pay2*20 pay3=pay3* 100 end when 'name2' then begin update table set pay2=pay2*20 pay3=pay3* 100 end when 'name3' then begin update table set pay3=pay3* 100 end end can u please tell the correct logic to complete the query using case statement 回答1: You'll have to swap the syntax around. The case statement will be applied for every