MySQL Lab 1 .? MySQL concurrency and Isolation Control Mechanism Meta-data metadata lock: Implemented in the tablecache cache, provides isolation operations for DDL (DataDefinitionLanguage. A special meta-data metadata type called NameLock. (SQL layer) table-level data lock (SQL layer) storage engine-specific mechanism ro
MySQL Lab 1 .? MySQL concurrency and Isolation Control Mechanism Meta-data metadata
: a mechanism that coordinates the concurrent access of multiple processes or threads to a resource. Lock conflict is an important factor that affects the performance of concurrent access to a database.The storage engine supports different locking mechanisms
Row lock
Table lock
Page lock
There are two lock classification methods.(1) from the perspective of the Database SystemThere are three types of locks:• Exclusive Lock)A resource with an exclusive lock can only be used by locked programs. Other operations on the resource are not accepted. SQL Server automatically uses an exclusive lock when executin
Keyboard events have two properties, KeyCode and CharCode, and there are a few differences between them. KeyCode indicates that the user presses the actual encoding of the key, while CharCode refers to the encoding of the user by pressing the character.ie underKeyCode: For the KeyPress event, the Unicode character that presses the key, or the numeric code that presses the key for the Keydown/keyup event.No
Keyboard events have two properties, KeyCode and CharCode, and there are a few differences between them. KeyCode indicates that the user presses the actual encoding of the key, while CharCode refers to the encoding of the user by pressing the character.ie underKeyCode: For the KeyPress event, the Unicode character that presses the key, or the numeric code that presses the key for the Keydown/keyup event.No
Firefox return key
Keycode (keypress) function key (shift, Ctrl, ALT, printscreen, scrolllock no return value) returns the correct value, all other key values are 0
Keycode (keydown) returns all the key values except printscreen. The primary key displays the key value (65-90) in the uppercase/lowercase state)
Keycode (keyup) returns all key values except print
As follows:Copy codeThe Code is as follows:TxtSearch: text box ID
$ ("# TxtSearch"). keyup (function (event ){Var keycode = event. which;If (keycode = 13 ){Alert ('you have pressed the enter key ');
}
});
Or
XObj. keyup (function (event ){// Obtain the key value of the current button// The jQuery event object has a which attribute to obtain the key value of the keyboard key.Var
OdiaeresisKeycode 250 = udiaeresis UdiaeresisKey code 251 = ssharp question backslashKeycode 252 = asciicircum degreeKeycode 253 = 3 sterlingKeycode 254 = Mode_switch UseCopy codeThe Code is as follows: Event. The keyCode value is 37, 38, 39, and 40. The cursor of the corresponding pressed direction is left, top, right, bottom."Javascript: if (event. keyCode If (event.
Connect to the SQL server lock mechanism (I)-Overview (lock type and scope)
Ii. Complete lock compatibility matrix (see)
Correct Code Description: see.
III. The following table lists the resources that can be locked by the database engine.
Name
Resources
Abbreviations
Encoding
Specifies the method to describe the resource when a
According to JS to determine the next key around:$ (document). On ("KeyUp", function (e) { var m_e = e | | window.event; var keycode = M_e.which; if (keycode = = = 38) { Window.console.log ("Up"); }else if (keycode = = = 40) { Window.console.log ("Down"); }else if (keycode = = = 37) {
I believe that all the friends who use VB know keycode and keyascii. Keycode parameters are included in keydown and keyup events, and keyascii parameters are included in keypress events. These two parameters are used in many cases.
I didn't know much about the differences between the two parameters. The only clear difference is that the keycode range is wider t
Keycode: obtains the enumeration of keys on the keyboard when the keydown or keyup is obtained.
KeyValue: Actually equal to keycode, keycode is enumeration, and keyValue is the integer value corresponding to enumeration.
Keydata: Get the keys value, which indicates the key code of the key to be pressed and the modifier sign (indicating the combination of Ctrl,
C # learning notes-KeyDown, KeyPress, KeyUp events, and KeyCode, KeyData, KeyValue, and KeyChar attributes,
I didn't plan to write it separately, but when I tested the mini-program myself, the more I wrote and found that I was not clear about it, the more I learned from it. So my practice once again proved that I had to think about it on paper, I am sure you want to do this!
Directly paste the Code:
1 // order of occurrence: keyDown-> KeyPress-> KeyUp
characters of the keypad and the main keyboard.6). Where Prscrn keys KeyPress, KeyDown, and KeyUp are not captured.KeyPress Event:private void Form1_keypress (object sender, KeyPressEventArgs e){if (e.keychar== ' 1 '){Button1. PerformClick ();//Perform the operation of button "1"E.handled = true;}}Keychar Value:2 additional special ASCII codes: Carriage return = 13, newline =10KeyDown event:private void Form1_keydown (object sender, KeyEventArgs e){Keys key = E.keycode;if (e.control!=true)//If
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