mysql 存储过程项目小结

1. false ：0  true 1 切记

官方文档：http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html

•  , 

  These types are synonyms for . A value of zero is considered false. Nonzero values are considered true:

  mysql> SELECT IF(0, ‘true‘, ‘false‘);
  +------------------------+
  | IF(0, ‘true‘, ‘false‘) |
  +------------------------+
  | false                  |
  +------------------------+
  
  mysql> SELECT IF(1, ‘true‘, ‘false‘);
  +------------------------+
  | IF(1, ‘true‘, ‘false‘) |
  +------------------------+
  | true                   |
  +------------------------+
  
  mysql> SELECT IF(2, ‘true‘, ‘false‘);
  +------------------------+
  | IF(2, ‘true‘, ‘false‘) |
  +------------------------+
  | true                   |
  +------------------------+

  However, the values TRUE and FALSE are merely aliases for 1 and 0, respectively, as shown here:

  mysql> SELECT IF(0 = FALSE, ‘true‘, ‘false‘);
  +--------------------------------+
  | IF(0 = FALSE, ‘true‘, ‘false‘) |
  +--------------------------------+
  | true                           |
  +--------------------------------+
  
  mysql> SELECT IF(1 = TRUE, ‘true‘, ‘false‘);
  +-------------------------------+
  | IF(1 = TRUE, ‘true‘, ‘false‘) |
  +-------------------------------+
  | true                          |
  +-------------------------------+
  
  mysql> SELECT IF(2 = TRUE, ‘true‘, ‘false‘);
  +-------------------------------+
  | IF(2 = TRUE, ‘true‘, ‘false‘) |
  +-------------------------------+
  | false                         |
  +-------------------------------+
  
  mysql> SELECT IF(2 = FALSE, ‘true‘, ‘false‘);
  +--------------------------------+
  | IF(2 = FALSE, ‘true‘, ‘false‘) |
  +--------------------------------+
  | false                          |
  +--------------------------------+

  The last two statements display the results shown because 2 is equal to neither 1 nor 0.

2 存储过程中执行动态sql

官方文档：

http://dev.mysql.com/doc/refman/5.0/en/sql-syntax-prepared-statements.html

The first example shows how to create a prepared statement by using a string literal to supply the text of the statement:

mysql> prePARE stmt1 FROM ‘SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse‘;
mysql> SET @a = 3;
mysql> SET @b = 4;
mysql> EXECUTE stmt1 USING @a, @b;
+------------+
| hypotenuse |
+------------+
|          5 |
+------------+
mysql> DEALLOCATE prePARE stmt1;

The second example is similar, but supplies the text of the statement as a user variable:

mysql> SET @s = ‘SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse‘;
mysql> prePARE stmt2 FROM @s;
mysql> SET @a = 6;
mysql> SET @b = 8;
mysql> EXECUTE stmt2 USING @a, @b;
+------------+
| hypotenuse |
+------------+
|         10 |
+------------+
mysql> DEALLOCATE prePARE stmt2;

Here is an additional example which demonstrates how to choose the table on which to perform a query at runtime, by storing the name of the table as a user variable:

mysql> USE test;
mysql> CREATE TABLE t1 (a INT NOT NULL);
mysql> INSERT INTO t1 VALUES (4), (8), (11), (32), (80);

mysql> SET @table = ‘t1‘;
mysql> SET @s = CONCAT(‘SELECT * FROM ‘, @table);

mysql> prePARE stmt3 FROM @s;
mysql> EXECUTE stmt3;
+----+
| a  |
+----+
|  4 |
|  8 |
| 11 |
| 32 |
| 80 |
+----+

mysql> DEALLOCATE prePARE stmt3;

总结：

执行动态sql，分三步走：

1. prePARE；

　Syntax：

prePARE stmt_name FROM preparable_stmt

2. EXECUTE；

　　 Syntax：

　　EXECUTE stmt_name [USING @var_name [, @var_name] ...]

3. DEALLOCATE prePARE；

　　Syntax：

{DEALLOCATE | DROP} prePARE stmt_name

 3. 存储过程中的事务

 语法：

START TRANSACTION [WITH CONSISTENT SNAPSHOT]
BEGIN [WORK]
COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
ROLLBACK [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
SET autocommit = {0 | 1}