There is only one way to know: Time it. In general, I think a single join enables the database to do a lot of optimizations, as it can see all the tables it needs to scan, overhead is reduced, and it can build up the result set locally. Recently, I had about 100 select-statements which … Read more
The “phantom read” in MySQL on RR isolation level is hidden deep, but still can reproduce it. Here are the steps: create table ab(a int primary key, b int); Tx1: begin; select * from ab; // empty set Tx2: begin; insert into ab values(1,1); commit; Tx1: select * from ab; // empty set, expected phantom … Read more
select * from MyTable where MyDate > DATEADD(year, -1, GetDate())
You ask if you can have more than one primary key field and you most certainly can. You can have only one primary key, but that can consist of as many columns as you need to uniquely identify your rows. Use something like this when you are creating your table: CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName) … Read more
As long as you have the right number of columns in your INSERT statement, and as long as all the values except KEYBOARD are some numeric data type, and as long as you have suitable permissions, this should work. INSERT INTO INVOICE VALUES( 1,1,’KEYBOARD’,1,15,5,75); SQL requires single quotes around text values. But not using column … Read more
Increase the linesize, e.g SET LINESIZE 32000 or use SET WRAP OFF (but this will truncate long values)
For MySql, Check in the EXTRA column: SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = ‘my_table’ AND COLUMN_NAME = ‘my_column’ AND DATA_TYPE = ‘int’ AND COLUMN_DEFAULT IS NULL AND IS_NULLABLE = ‘NO’ AND EXTRA like ‘%auto_increment%’ For Sql Server, use sys.columns and the is_identity column: SELECT is_identity FROM sys.columns WHERE object_id = object_id(‘my_table’) AND name=”my_column”
I think that you are after this: SELECT image_id FROM list WHERE (style_id, style_value) IN ((24,’red’),(25,’big’),(27,’round’)) GROUP BY image_id HAVING count(distinct style_id, style_value)=3 You can’t use AND, because values can’t be 24 red and 25 big and 27 round at the same time in the same row, but you need to check the presence of … Read more
Have you tried the solutions presented here: Convert JS date time to MySQL datetime The title should be called “Convert JS date to SQL DateTime” I happened to need to do the same thing as you just now and I ran across this after your question. This is from the other post by Gajus Kuizinas … Read more
Change your first statement to this pstat=con.prepareStatement(“select typeid from users where username=? and password=?”, ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE); This way you can move forward and backward, so less things to worry about