Mysql CHAR vs VARCHAR Post: 302144157

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LEARN ABOUT PHP

sql-acceptable-by-4d

SQL-ACCEPTABLE-BY-4D(3) 						 1						   SQL-ACCEPTABLE-BY-4D(3)

SQL acceptable by 4D - PDO and SQL 4D

	4D  implements	strictly  the  ANSI  89 standard, and have it enforced. It is highly recommended to read the 4D SQL documentation to learn
       about the available commands. The URL of the manual is : http://doc.4d.com/. Below is a list of 4D SQL characteristics: it is  not  exhaus-
       tive, but may serve as an introduction.

       Characteristics of 4D SQL

       +-------------------------------------+--------------------------------------+---+
       |	  Characteristics	     |					    |	|
       |				     |					    |	|
       |				     |		   Alternative		    |	|
       |				     |					    |	|
       |				     |		       Note		    |	|
       |				     |					    |	|
       +-------------------------------------+--------------------------------------+---+
       |	      INTEGER		     |					    |	|
       |				     |					    |	|
       |				     |	    Modify the SQL to use INT.	    |	|
       |				     |					    |	|
       |				     | INT is the supported integer type in |	|
       |				     | 4Dv12.0. 			    |	|
       |				     |					    |	|
       |		CHAR		     |					    |	|
       |				     |					    |	|
       |				     |	       Use VARCHAR instead.	    |	|
       |				     |					    |	|
       |				     |	      Unsupported in 4Dv12.0	    |	|
       |				     |					    |	|
       |	       UNION		     |					    |	|
       |				     |					    |	|
       |				     | Unsupported. Make separate queries.  |	|
       |				     |					    |	|
       |				     |	      Unsupported in 4Dv12.0	    |	|
       |				     |					    |	|
       |	   SELECT 1 + 1;	     |					    |	|
       |				     |					    |	|
       |				     |	 SELECT 1 + 1 FROM _USER_SCHEMAS;   |	|
       |				     |					    |	|
       |				     |		 FROM is required	    |	|
       |				     |					    |	|
       |	       FLOAT		     |					    |	|
       |				     |					    |	|
       |				     | Cast the FLOAT value into a FLOAT or |	|
       |				     | STRING,	with  an  SQL  4D  function |	|
       |				     | (CAST, ROUND, TRUNC or TRUNCATE)     |	|
       |				     |					    |	|
       |				     | Unsupported in current  versions  of |	|
       |				     | the PDO_4D driver		    |	|
       |				     |					    |	|
       |	   Strong typing	     |					    |	|
       |				     |					    |	|
       |				     | Take  care  your  SQL query, or your |	|
       |				     | PHP  code  provides  data  with	the |	|
       |				     | expected type			    |	|
       |				     |					    |	|
       |				     |	One  must  provide  the  right type |	|
       |				     | that 4D expect. One can't insert '1' |	|
       |				     | (as a string) in an INTEGER column.  |	|
       |				     |					    |	|
       |PDO.execute(row)(3)  : only works if |					    |	|
       |all the table's column are  of	type |					    |	|
       |TEXT or VARCHAR 		     |					    |	|
       |				     |					    |	|
       |				     | Use the prepared statements, and use |	|
       |				     | the right types. 		    |	|
       |				     |					    |	|
       |				     | The PDO extension  cast	all  values |	|
       |				     | through	execute()  as  string,	and |	|
       |				     | expect the SQL database to parse the |	|
       |				     | values.				    |	|
       |				     |					    |	|
       |       SELECT NULL FROM TABLE	     |					    |	|
       |				     |					    |	|
       |				     | Do  not	use NULL constants. Extract |	|
       |				     | them from the table		    |	|
       |				     |					    |	|
       |				     | It is not allowed to  use  the  NULL |	|
       |				     | constant in the select list	    |	|
       |				     |					    |	|
       |    SELECT * FROM TABLE WHERE 1      |					    |	|
       |				     |					    |	|
       |				     |		 Use WHERE 1 = 1	    |	|
       |				     |					    |	|
       |				     | A  constant can't be used in a WHERE |	|
       |				     | clause				    |	|
       |				     |					    |	|
       |	    SHOW TABLES 	     |					    |	|
       |				     |					    |	|
       |				     |		Use system tables	    |	|
       |				     |					    |	|
       |				     |	The list of tables, schemas, index, |	|
       |				     | etc.  are  in  these system tables : |	|
       |				     | _USER_TABLES,	     _USER_COLUMNS, |	|
       |				     | _USER_INDEXES,	 _USER_CONSTRAINTS, |	|
       |				     | _USER_IND_COLUMNS,   _USER_CONS_COL- |	|
       |				     | UMNS, and _USER_SCHEMAS. 	    |	|
       |				     |					    |	|
       |      SQL structure delimiter	     |					    |	|
       |				     |					    |	|
       |				     |	Use  the following function to pro- |	|
       |				     | tect    SQL    elements:    function |	|
       |				     | sqlEscapeElement(elem)  { return '[' |	|
       |				     | .  str_replace(']',']]',  $elem)   . |	|
       |				     | ']'; }				    |	|
       |				     |					    |	|
       |				     |	To   escape   SQL   elements  names |	|
       |				     | (tables,  fields,   users,   groups, |	|
       |				     | schema,	 primary  key,	etc.),	the |	|
       |				     | whole  identifier  must	be  between |	|
       |				     | square  brackets,  and  the  closing |	|
       |				     | brackets ']' must be doubled.	    |	|
       |				     |					    |	|
       +-------------------------------------+--------------------------------------+---+
PHP Documentation Group 												   SQL-ACCEPTABLE-BY-4D(3)