triggers

问题 I have the following questions regarding BLOBs in sqlite: Does sqlite keep track of sizes of BLOBs? I'm guessing that it does, but then, does the length function use it, or does it read the BLOB's content? If sqlite keeps track of the size of the BLOB and length doesn't use it, is the size accessible via some other functionality? I'm asking this because I'm wondering if I should implement triggers that set BLOBs' sizes in additional columns, of if I can obtain the sizes dynamically without

问题 I am trying to figure out make a trigger to assign the value of the auto incremented 'ID' primary key field that is auto generated upon insert to another field 'Sort_Placement' so they are the same after insert. If you are wondering why I am doing this, 'Sort_Placement' is used as a sort value in a table that can be changed but by default the record is added to the bottom of the table Table Data `ID` mediumint(8) unsigned NOT NULL AUTO_INCREMENT, `Account_Num` mediumint(8) unsigned NOT NULL,

问题 I'm having the darndest time figuring this out: say I've got two Button and three TextBlocks. I want either button to trigger a simple Storyboard on ALL TextBlocks. Currently I'm trying to define a generic Textblock style that contains the Storyboard, and then the trigger comes from any Button click. This is the closest I've come but the app crashes on startup...what am I don't wrong here: <Window.Resources> <Style TargetType="TextBlock" > <Setter Property="Foreground" Value="Blue" /> <Style

问题 I am using MySQL. My question is how to automatically insert the newly added row into a foreign-key table. An example will clarify my question: I have two tables Employee and Salary: CREATE TABLE Employee( emp_id int NOT NULL AUTO_INCREMENT, name char(30), PRIMARY KEY (emp_id) ) ENGINE=innoDB; CREATE TABLE salary { sal_id int NOT NULL AUTO_INCREMENT salary_figure int, emp_id int, PRIMARY KEY (sal_id), FOREIGN KEY REFERENCES Employee(emp_id) } Here is the join table : employee_salary_join

问题 Pretty general question regarding triggers in SQL server 2005. In what situations are table triggers fired and what situations aren't they? Any code examples to demonstrate would be great. I'm writing a audit based databases and just want to be aware of any situations that might not fire off the triggers that I have set up for update, delete and insert on my tables. A example of what I mean, UPDATE MyTable SET name = 'test rows' WHERE id in (1, 2, 3); The following statement only fires the

问题 I have a status message located on the first row of my grid and I want it to slide in and out when the visibility changes. The first visibility trigger works great and slides the first grid row open quickly. As soon as I add the 'Collapsed' trigger, nothing works at all. How do I reverse the animation to slide closed when the visibility is set to collapsed? <Grid Grid.Row="0" Height="55" Visibility="{Binding StatusMessageVisibility, Mode=TwoWay}"> <Grid.Style> <Style TargetType="Grid"> <Style

问题 Instagram's Postgres method of implementing custom Ids for Sharding is great, but I need the implementation in MySQL. So, I converted the method found at the bottom of this blog, here: http://instagram-engineering.tumblr.com/post/10853187575/sharding-ids-at-instagram MySQL Version: CREATE TRIGGER shard_insert BEFORE INSERT ON tablename FOR EACH ROW BEGIN DECLARE seq_id BIGINT; DECLARE now_millis BIGINT; DECLARE our_epoch BIGINT DEFAULT 1314220021721; DECLARE shard_id INT DEFAULT 1; SET now

问题 I'm trying to get a 'date' type that corresponds to the first day of the current month. Basically one of my tables stores a date, but I want it to always be the first of the month, so I'm trying to create a trigger that will get now() and then replace the day with a 1. 回答1: You can use the expression date_trunc('month', current_date) . Demonstrated with a SELECT statement . . . select date_trunc('month', current_date) 2013-08-01 00:00:00-04 To remove time, cast to date. select cast(date_trunc

问题 I have the below trigger: CREATE Trigger enroll_limit on Enrollments Instead of Insert As Declare @Count int Declare @Capacity int Select @Count = COUNT(*) From Enrollments Select @Capacity = Capacity From CourseSections If @Count < @Capacity Begin Insert Into Enrollments Select * From Inserted End GO I'm getting an error msg saying: 'CREATE TRIGGER' must be the first statement in a query batch. 回答1: The error message "'CREATE TRIGGER' must be the first statement in a query batch." usually

问题 I am trying to implement the equivalent of the "ON UPDATE CURRENT_TIMESTAMP" MySQL feature in sqlite. My idea it to use a trigger like this: CREATE TRIGGER last_update_trigger AFTER UPDATE ON mytable FOR EACH ROW BEGIN UPDATE mytable SET last_update = CURRENT_TIMESTAMP WHERE id = old.id; END But there's a problem with this. Each time an update occurs on a record of this table, the trigger triggers a new update on this same record. This should trigger the trigger again, and again, leading to