reference_option: RESTRICT | CASCADE | SET NULL | NO ACTION
index_namerepresents a foreign key ID. If given, this is ignored if an index for the foreign key is defined explicitly. Otherwise, ifcreates an index for the foreign key, it usesindex_namefor the index name.
Foreign keys definitions are subject to the following conditions:
Both tables must betables and they must not beTEMPORARYtables.
Corresponding columns in the foreign key and the referenced key must have similar internal data types insideInnoDBso that they can be compared without a type conversion.The size and sign of integer types must be the same. The length of string types need not be the same. For nonbinary (character) string columns, the character set and collation must be the same.
InnoDBrequires indexes on foreign keys and referenced keys so that foreign key checks can be fast and not require a table scan. In the referencing table, there must be an index where the foreign key columns are listed as thefirstcolumns in the same order. Such an index is created on the referencing table automatically if it does not exist. (This is in contrast to some older versions, in which indexes had to be created explicitly or the creation of foreign key constraints would fail.)index_name, if given, is used as described previously.
InnoDBallows a foreign key to reference any index column or group of columns. However, in the referenced table, there must be an index where the referenced columns are listed as thecolumns in the same order.
Index prefixes on foreign key columns are not supported. One consequence of this is thatBLOBandTEXTcolumns cannot be included in a foreign key because indexes on those columns must always include a prefix length.
If theCONSTRAINTsymbolclause is given, thesymbolvalue must be unique in the database. If the clause is not given,InnoDBcreates the name automatically.
InnoDBrejects anyINSERTorUPDATEoperation that attempts to create a foreign key value in a child table if there is no a matching candidate key value in the parent table. The actionInnoDBtakes for anyUPDATEorDELETEoperation that attempts to update or delete a candidate key value in the parent table that has some matching rows in the child table is dependent on thespecified usingON UPDATEandON DELETEsubclauses of theFOREIGN KEYclause. When the user attempts to delete or update a row from a parent table, and there are one or more matching rows in the child table,InnoDBsupports five options regarding the action to be taken. IfON DELETEorON UPDATEare not specified, the default action isRESTRICT.
CASCADE: Delete or update the row from the parent table and automatically delete or update the matching rows in the child table. BothON DELETE CASCADEandON UPDATE CASCADEare supported. Between two tables, you should not define severalON UPDATE CASCADEclauses that act on the same column in the parent table or in the child table.
Note
Currently, cascaded foreign key actions to not activate triggers.
SET NULL: Delete or update the row from the parent table and set the foreign key column or columns in the child table toNULL. This is valid only if the foreign key columns do not have theNOT NULLqualifier specified. BothON DELETE SET NULLandON UPDATE SET NULLclauses are supported.
If you specify aSET NULLaction,make sure that you have not declared the columns in the child table asNOT NULL.
NO ACTION: In standard SQL,NO ACTIONmeansno actionin the sense that an attempt to delete or update a primary key value is not allowed to proceed if there is a related foreign key value in the referenced table.InnoDBrejects the delete or update operation for the parent table.
RESTRICT: Rejects the delete or update operation for the parent table. SpecifyingRESTRICT(orNO ACTION) is the same as omitting theON DELETEorON UPDATEclause. (Some database systems have deferred checks, andNO ACTIONis a deferred check. In MySQL, foreign key constraints are checked immediately, soNO ACTIONis the same asRESTRICT.)
SET DEFAULT: This action is recognized by the parser, butInnoDBrejects table definitions containingON DELETE SET DEFAULTorON UPDATE SET DEFAULTclauses.
InnoDBsupports foreign key references within a table. In these cases, “child table records” really refers to dependent records within the same table.
Here is a simple example that relatesparentandchildtables through a single-column foreign key:
CREATE TABLE parent (id INT NOT NULL, PRIMARY KEY (id) ) ENGINE=INNODB;
CREATE TABLE child (id INT, parent_id INT, INDEX par_ind (parent_id), FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE ) ENGINE=INNODB;
A more complex example in which aproduct_ordertable has foreign keys for two other tables. One foreign key references a two-column index in theproducttable. The other references a single-column index in thecustomertable:
CREATE TABLE product (category INT NOT NULL, id INT NOT NULL, price DECIMAL, PRIMARY KEY(category, id)) ENGINE=INNODB;
CREATE TABLE customer (id INT NOT NULL, PRIMARY KEY (id)) ENGINE=INNODB;
CREATE TABLE product_order (no INT NOT NULL AUTO_INCREMENT, product_category INT NOT NULL, product_id INT NOT NULL, customer_id INT NOT NULL, PRIMARY KEY(no), INDEX (product_category, product_id), FOREIGN KEY (product_category, product_id) REFERENCES product(category, id) ON UPDATE CASCADE ON DELETE RESTRICT, INDEX (customer_id), FOREIGN KEY (customer_id) REFERENCES customer(id)) ENGINE=INNODB;
Developer Riot Games announces new MMO game titled League of Legends which combines aspects of role-playing and strategy games popular as DOTA all star. Was released on the public after this game can be a substitute for DOTA? Only time can talk. Welcome to the new round of competitive online gaming.
You will act as a Summoner who can bring a hero to champion the battle. Together with the NPC ally, you must use tactics to defeat the other in a battle Summoner very similar to DotA.
This latest online game, is really similar to DOTA all star, the difference, the DOTA is a mod of warcraft3 while, the League of Legends is an online game actually stand alone.Just like DotA, League of Legends in this, your team will control the Hero in tactics and strategy in defeating the other team's hero.Each hero class has its own unique skills.
For business graphics, new games are obviously better than DotA game that was released many years. But whether this game could replace DOTA??
No special classes or libraries are used with this application. The complete source resides in the one file above. After downloading, the following should work in any JDK 1.2 compatible compiler:
javac MatrixCalculator.java java MatrixCalculator
Matrix Calculator Tips/Help
All Matrices must be symmetric (n x n) Enter Matrix Elements Row by Row seperated by spaces. Ex. (2x2) 2 4
3 1
Results will be placed in the C matrix.
The calculation of the determinant, by definition, is based upon a factorial number of calculations with respect to the size of the matrix. ie. a 3x3 matrix would have 6 calculations (3!) to make, whereas a 20x20 matrix would have 2.43 x 10^18 calculations (20!). So instead of brute forcing the calculations, I first do some operations on the matrix, which converts it to a upper triangular matrix, and then calculate the determinant by multipling down the diagonal, since everything below is 0, this will give the determinant.
Floating Points and Accuracies
For some reason computers aren't as accurate as I think they are, probably my calculation techniques. The accuracy of the numbers are probably only to 3 maybe 2 decimal places. If you keep applying operations to matrices and then use the resultant matrix a couple of times, the decimals get out of whack. Calculating an inverse and then multplying the matrix by it, is a good example of this.
Test Some Mathematical Theories
The determinant of A-inverse equals 1 over the determinant of A.
If two rows of matrix A are equal, the determinant of A equals 0.
det(A*B)=det(A)det(B)
A*B does not necessarily equal B*A
The determinant of A-transpose equals the determinant of A.
If the matrix B is constructed by interchanging two rows (columns) in matrix A, then the determinant of B equals the negative determinant of A
You can test, adj(A) = det(A) * inv(A), but this is the theorem I use to calculate the inverse, so it better work.
Mathematics and Linear Algebra Calculating the Determinant
The calculation of the determinant, by definition, is based upon a factorial number of calculations with respect to the size of the matrix. ie. a 3x3 matrix would have 6 calculations (3!), whereas a 20x20 matrix would have 2.43 x 10^18 calculations (20!).
So instead of brute forcing the calculations, I first do some operations on the matrix, which converts it to a upper triangular matrix, and then calculate the determinant by multipling down the diagonal, since everything below is 0, this will give the determinant.
See The Mathematics Behind Them for more information and mathematical explanations on the definitions and calculation techniques.
Click the spoiler below for displaying source-code
if (DEBUG) System.out.println("Baris: " + ts.countTokens());
float matrix[][] = new float[ts.countTokens()][];
StringTokenizer st2; int row = 0; int col = 0; //making sure rows are same length int last = -5; int curr = -5; while (ts.hasMoreTokens()) { st2 = new StringTokenizer(ts.nextToken(), " "); last = curr; curr = st2.countTokens(); if(last != -5 && curr!= last) throw new Exception("Baris != length"); if (DEBUG) System.out.println("Kolom: " + st2.countTokens()); matrix[row] = new float[st2.countTokens()]; while (st2.hasMoreElements()) { matrix[row][col++] = Float.parseFloat(st2.nextToken()); } row++; col = 0; } System.out.println(); return matrix; }
// -------------------------------------------------------------- // Display Matrix in TextArea // -------------------------------------------------------------- public void DisplayMatrix(float[][] matrix, JTextArea ta) {
if (DEBUG) { System.out.println("Displaying Matrix"); }
String rstr = ""; String dv = "";
for (int i = 0; i < matrix.length; i++) { for (int j = 0; j < matrix[i].length; j++) { dv = nf.format(matrix[i][j]); rstr = rstr.concat(dv + " "); }
rstr = rstr.concat("\n"); }
ta.setText(rstr); }
public float[][] AddMatrix(float[][] a, float[][] b) throws Exception { int tms = a.length; int tmsB = b.length; if (tms != tmsB) { statusBar.setText("Matrix Size Mismatch"); }
float matrix[][] = new float[tms][tms];
for (int i = 0; i < tms; i++) for (int j = 0; j < tms; j++) { matrix[i][j] = a[i][j] + b[i][j]; }
return matrix; }
// -------------------------------------------------------------- public float[][] MultiplyMatrix(float[][] a, float[][] b) throws Exception {
if(a[0].length != b.length) throw new Exception("Matrices incompatible for multiplication"); float matrix[][] = new float[a.length][b[0].length];
for (int i = 0; i < a.length; i++) for (int j = 0; j < b[i].length; j++) matrix[i][j] = 0;
//cycle through answer matrix for(int i = 0; i < matrix.length; i++){ for(int j = 0; j < matrix[i].length; j++){ matrix[i][j] = calculateRowColumnProduct(a,i,b,j); } } return matrix; }
public float calculateRowColumnProduct(float[][] A, int row, float[][] B, int col){ float product = 0; for(int i = 0; i < A[row].length; i++) product +=A[row][i]*B[i][col]; return product; } // --------------------------------------------------------------
public float[][] Transpose(float[][] a) { if (INFO) { System.out.println("Performing Transpose..."); }
float m[][] = new float[a[0].length][a.length];
for (int i = 0; i < a.length; i++) for (int j = 0; j < a[i].length; j++) m[j][i] = a[i][j]; return m; }
public float[][] Inverse(float[][] a) throws Exception { // Formula used to Calculate Inverse: // inv(A) = 1/det(A) * adj(A) if (INFO) { System.out.println("Performing Inverse..."); } int tms = a.length;
float m[][] = new float[tms][tms]; float mm[][] = Adjoint(a);
float det = Determinant(a); float dd = 0;
if (det == 0) { statusBar.setText("Determinant = 0, Not Invertible."); if (INFO) { System.out.println("Determinant = 0, Not Invertible."); } } else { dd = 1 / det; }
for (int i = 0; i < tms; i++) for (int j = 0; j < tms; j++) { m[i][j] = dd * mm[i][j]; }
