The JDBC specification defines functions with an escape call syntax :
{fn function_name(arguments)}. The following tables show
which functions are supported by the LightDB™ driver. The driver
supports the nesting and the mixing of escaped functions and escaped
values. The appendix C of the JDBC specification describes the
functions.
Some functions in the following tables are translated but not
reported as supported because they are duplicating or changing their
order of the arguments. While this is harmless for literal values or
columns, it will cause problems when using prepared statements. For
example “{fn right(?,?)}” will be translated to
“substring(? from (length(?)+1-?))”. As you can see the
translated SQL requires more parameters than before the translation but
the driver will not automatically handle this.
Table 8.1. Supported escaped numeric functions
| function | reported as supported | translation | comments |
|---|---|---|---|
| abs(arg1) | yes | abs(arg1) | |
| acos(arg1) | yes | acos(arg1) | |
| asin(arg1) | yes | asin(arg1) | |
| atan(arg1) | yes | atan(arg1) | |
| atan2(arg1,arg2) | yes | atan2(arg1,arg2) | |
| ceiling(arg1) | yes | ceil(arg1) | |
| cos(arg1) | yes | cos(arg1) | |
| cot(arg1) | yes | cot(arg1) | |
| degrees(arg1) | yes | degrees(arg1) | |
| exp(arg1) | yes | exp(arg1) | |
| floor(arg1) | yes | floor(arg1) | |
| log(arg1) | yes | ln(arg1) | |
| log10(arg1) | yes | log(arg1) | |
| mod(arg1,arg2) | yes | mod(arg1,arg2) | |
| pi(arg1) | yes | pi(arg1) | |
| power(arg1,arg2) | yes | pow(arg1,arg2) | |
| radians(arg1) | yes | radians(arg1) | |
| rand() | yes | random() | |
| rand(arg1) | yes | setseed(arg1)*0+random() | The seed is initialized with the given argument and a new randow value is returned. |
| round(arg1,arg2) | yes | round(arg1,arg2) | |
| sign(arg1) | yes | sign(arg1) | |
| sin(arg1) | yes | sin(arg1) | |
| sqrt(arg1) | yes | sqrt(arg1) | |
| tan(arg1) | yes | tan(arg1) | |
| truncate(arg1,arg2) | yes | trunc(arg1,arg2) |
Table 8.2. Supported escaped string functions
| function | reported as supported | translation | comments |
|---|---|---|---|
| ascii(arg1) | yes | ascii(arg1) | |
| char(arg1) | yes | chr(arg1) | |
| concat(arg1,arg2…) | yes | (arg1||arg2…) | The JDBC specification only require the two arguments version, but supporting more arguments was so easy… |
| insert(arg1,arg2,arg3,arg4) | no | overlay(arg1 placing arg4 from arg2 for arg3) | This function is not reported as supported since it changes the order of the arguments which can be a problem (for prepared statements by example). |
| lcase(arg1) | yes | lower(arg1) | |
| left(arg1,arg2) | yes | substring(arg1 for arg2) | |
| length(arg1) | yes | length(trim(trailing from arg1)) | |
| locate(arg1,arg2) | no | position(arg1 in arg2) | |
| locate(arg1,arg2,arg3) | no | (arg2*sign(position(arg1 in substring(arg2 from arg3)+position(arg1 in substring(arg2 from arg3)) | Not reported as supported since the three arguments version duplicate and change the order of the arguments. |
| ltrim(arg1) | yes | trim(leading from arg1) | |
| repeat(arg1,arg2) | yes | repeat(arg1,arg2) | |
| replace(arg1,arg2,arg3) | yes | replace(arg1,arg2,arg3) | Only reported as supported by 7.3 and above servers. |
| right(arg1,arg2) | no | substring(arg1 from (length(arg1)+1-arg2)) | Not reported as supported since arg2 is duplicated. |
| rtrim(arg1) | yes | trim(trailing from arg1) | |
| space(arg1) | yes | repeat(’ ’,arg1) | |
| substring(arg1,arg2) | yes | substr(arg1,arg2) | |
| substring(arg1,arg2,arg3) | yes | substr(arg1,arg2,arg3) | |
| ucase(arg1) | yes | upper(arg1) | |
| soundex(arg1) | no | soundex(arg1) | Not reported as supported since it requires the fuzzystrmatch contrib module. |
| difference(arg1,arg2) | no | difference(arg1,arg2) | Not reported as supported since it requires the fuzzystrmatch contrib module. |
Table 8.3. Supported escaped date/time functions
| function | reported as supported | translation | comments |
|---|---|---|---|
| curdate() | yes | current_date | |
| curtime() | yes | current_time | |
| dayname(arg1) | yes | to_char(arg1,‘Day’) | |
| dayofmonth(arg1) | yes | extract(day from arg1) | |
| dayofweek(arg1) | yes | extract(dow from arg1)+1 | We must add 1 to be in the expected 1-7 range. |
| dayofyear(arg1) | yes | extract(doy from arg1) | |
| hour(arg1) | yes | extract(hour from arg1) | |
| minute(arg1) | yes | extract(minute from arg1) | |
| month(arg1) | yes | extract(month from arg1) | |
| monthname(arg1) | yes | to_char(arg1,‘Month’) | |
| now() | yes | now() | |
| quarter(arg1) | yes | extract(quarter from arg1) | |
| second(arg1) | yes | extract(second from arg1) | |
| week(arg1) | yes | extract(week from arg1) | |
| year(arg1) | yes | extract(year from arg1) | |
| timestampadd(argIntervalType,argCount,argTimeStamp) | yes | (‘(interval according to argIntervalType and argCount)’+argTimeStamp) | an argIntervalType value of SQL_TSI_FRAC_SECOND is not implemented since backend does not support it |
| timestampdiff(argIntervalType,argTimeStamp1,argTimeStamp2) | not | extract((interval according to argIntervalType) from argTimeStamp2-argTimeStamp1 ) | only an argIntervalType value of SQL_TSI_FRAC_SECOND, SQL_TSI_FRAC_MINUTE, SQL_TSI_FRAC_HOUR or SQL_TSI_FRAC_DAY is supported |
Table 8.4. Supported escaped misc functions
| function | reported as supported | translation | comments |
|---|---|---|---|
| database() | yes | current_database() | Only reported as supported by 7.3 and above servers. |
| ifnull(arg1,arg2) | yes | coalesce(arg1,arg2) | |
| user() | yes | user |