How to convert MS SQL queries into MySQL format
|[SQL Server to MySQL Converter] [About Migration] [Safe Types Mapping] [Stored Procedures]|
When migrating databases from MS SQL to MySQL server it is often necessary to translate MS SQL queries according to MySQL syntax as well. Syntax of SQL queries in MS SQL and MySQL are similar but not identical. This article discovers 10 most popular differences between MS SQL and MySQL syntax. The target audience for this guide should have general database management knowledge and experience in composing SQL queries.
Also, MS SQL provides effective solution to avoid naming objects conflict
and to manage user permissions on data access. This is schema, a logic
container used to group and categorize objects inside the single database.
When using schema the full name of database object in query may look like
database.schema.object. However, there is no such semantic in MySQL,
so all schema names must be cut off from queries.
CHARINDEXto search substring into string. MySQL equivalent for this function is
CONVERT()function is used to convert an expression of one data type to another in MS SQL. In MySQL
CONVERT()function converts text data between different character sets. However, there is equivalent function
CAST(), so every occurrence of
convert(type, expression)in MS SQL query must be replaced by
cast(expression AS type)in MySQL query.
IIF($boolean_expression, $true_value, $false_value)that returns $true_value or $false_value value depending on $boolean_expression, must be replaced by
LEN()function returns length of string expression in MS SQL. MySQL equivalent for this function is
DATEADDadds interval to the specified part of the date. MySQL operator
'+'can do the same as follows:
DATEADD(year, 1, $date$) -> $date$ + interval 1 year DATEADD(month, 1, $date$) -> $date$ + interval 1 month DATEADD(day, 1, $date$) -> $date$ + interval 1 day
where $date$ is an expression of DATE type. Function
$startdate, $enddate) returns $datepart part of substructing $startdate
from $enddate. It can be converted into MySQL as follows:
DATEDIFF(hour, $startdate, $enddate) -> TIMESTAMPDIFF(hour, $enddate, $startdate) DATEDIFF(minute, $startdate, $enddate) -> TIMESTAMPDIFF(minute, $enddate, $startdate) DATEDIFF(month, $startdate, $enddate) -> TIMESTAMPDIFF(month, $enddate, $startdate)
In general, Microsoft SQL and MySQL have different sets of date processing functions, although most of them can be replicated as follows:
DATENAME(month, $date$) -> DATE_FORMAT($date$, '%M') or MONTHNAME(expression) DATENAME(weekday, $date$) -> DATE_FORMAT($date$, '%W') or DAYNAME(expression) DATEPART(year, $date$) -> DATE_FORMAT($date$, '%Y') DATEPART(month, $date$) -> DATE_FORMAT($date$, '%m') DATEPART(day, $date$) -> DATE_FORMAT($date$, '0') GETDATE() -> NOW() GETUTCDATE() -> UTC_TIMESTAMP()
where $date$ is an expression of DATE type.
'+'allows to concatenate strings like this:
'string1' + 'string2'. In MySQL such expressions must be replaced by
CONTAINS(expression, template)searches for matches of template inside expression. MySQL has operator
LIKEthat implements the same semantics:
expression LIKE %template%
'TOP (100) PERCENT'pattern just cut it off when composing MySQL query. If there is another percentage amount in that pattern, it can be replace by the following code in MySQL (works in MySQL 5.0.7 and higher):
SET @amount =(SELECT COUNT(*) FROM %table name%) * %percentage% / 10; PREPARE STMT FROM '%original query% FROM %table name% LIMIT ?'; EXECUTE STMT USING @amount;
JOINconstructions are very similar in MS SQL and MySQL. The only difference is that MS SQL keyword
WHEREis replaced by
ONin MySQL. For example:
... table1 CROSS JOIN table2 WHERE conditionmust be translated into
... table1 CROSS JOIN table2 ON condition
More articles about MS SQL, MySQL and other databases can be found at http://www.convert-in.com/articles.htm