diff --git a/src/TulipaIO.jl b/src/TulipaIO.jl
index c26badc..24d9659 100644
--- a/src/TulipaIO.jl
+++ b/src/TulipaIO.jl
@@ -1,5 +1,6 @@
 module TulipaIO
 
+include("exceptions.jl")
 include("parsers.jl")
 include("pipeline.jl")
 
diff --git a/src/exceptions.jl b/src/exceptions.jl
new file mode 100644
index 0000000..2145baa
--- /dev/null
+++ b/src/exceptions.jl
@@ -0,0 +1,45 @@
+import DuckDB: DB
+
+struct FileNotFoundError <: Exception
+    file::String
+    msg::String
+    function FileNotFoundError(file)
+        if ispath(file)
+            new(file, "$(file): exists, but not a regular file")
+        else
+            new(file, "$(file): file not found")
+        end
+    end
+end
+
+struct DirectoryNotFoundError <: Exception
+    dir::String
+    msg::String
+    function DirectoryNotFoundError(dir)
+        if ispath(dir)
+            new(dir, "$(dir): exists, but not a directory")
+        else
+            new(dir, "$(dir): directory not found")
+        end
+    end
+end
+
+struct TableNotFoundError <: Exception
+    con::DB
+    tbl::String
+    msg::String
+    TableNotFoundError(con, tbl) = new(con, tbl, "$(tbl): table not found in $(con)")
+end
+
+struct NeitherTableNorFileError <: Exception
+    con::DB
+    src::String
+    msg::String
+    NeitherTableNorFileError(con, src, msg) =
+        new(con, src, "$(src): neither table ($con) nor file found")
+end
+
+Base.showerror(io::IO, exc::FileNotFoundError) = print(io, exc.msg)
+Base.showerror(io::IO, exc::DirectoryNotFoundError) = print(io, exc.msg)
+Base.showerror(io::IO, exc::TableNotFoundError) = print(io, exc.msg)
+Base.showerror(io::IO, exc::NeitherTableNorFileError) = print(io, exc.msg)
diff --git a/src/fmtsql.jl b/src/fmtsql.jl
new file mode 100644
index 0000000..5d3999a
--- /dev/null
+++ b/src/fmtsql.jl
@@ -0,0 +1,62 @@
+module FmtSQL
+
+function sprintf(fmt::String, args...)
+    format(Format(fmt), args...)
+end
+
+function fmt_opts(source::String; opts...)
+    _src = '?' in source ? "$source" : "'$(source)'"
+    join(["$(_src)"; [join(p, "=") for p in opts]], ", ")
+end
+
+function reader(source::String)
+    _, ext = splitext(source)
+    if ext in (".csv", ".parquet", ".json")
+        return "read_$(ext[2:end])_auto"
+    elseif '?' in source
+        # FIXME: how to support other file formats?
+        return "read_csv_auto"
+    else
+        error("$(ext[2:end]): unsupported input file '$(source)'")
+    end
+end
+
+function fmt_read(source::String, opts...)
+    sprintf("%s(%s)", reader(source), fmt_opts(source; opts...))
+end
+
+function fmt_select(source::String; opts...)
+    sprintf("SELECT * FROM %s", fmt_read(source; opts...))
+end
+
+function fmt_join(
+    from_subquery::String,
+    join_subquery::String;
+    on::Vector{String},
+    cols::Vector{String},
+    fill::Union{Bool,Vector::Any},
+)
+    exclude = join(cols, ", ")
+    if fill       # back fill
+        # e.g.: IFNULL(t2.investable, t1.investable) AS investable
+        include = join(map(c -> "IFNULL(t2.$c, t1.$c) AS $c", cols), ", ")
+    elseif !fill # explicit missing
+        include = join(map(c -> "t2.$c", cols), ", ")
+    else          # fill with default
+        if length(fill) != length(cols)
+            msg = "number of default values does not match columns\n"
+            msg = msg * "columns: $cols\n"
+            msg = msg * "defaults: $fill"
+            error(msg)
+        end
+        include = join(map((c, f) -> "IFNULL(t2.$c, $f) AS $c", zip(cols, fill)), ", ")
+    end
+    select_ = "SELECT t1.* EXCLUDE ($exclude), $include"
+
+    join_on = join(map(c -> "t1.$c = t2.$c", on), " AND ")
+    from_ = "FROM $from_subquery t1 LEFT JOIN $join_subquery t2 ON ($join_on)"
+
+    "$(select_)\n$(from_)"
+end
+
+end # module FmtSQL
diff --git a/src/pipeline.jl b/src/pipeline.jl
index b29162f..f9cd17b 100644
--- a/src/pipeline.jl
+++ b/src/pipeline.jl
@@ -2,66 +2,29 @@ using DataFrames: DataFrames as DF
 using DuckDB: DB, DBInterface, Stmt
 using Printf: format, Format
 
-function sprintf(fmt::String, args...)
-    format(Format(fmt), args...)
-end
+using .FmtSQL: fmt_join, fmt_read, fmt_select
 
-function fmt_opts(source::String; opts...)
-    _src = '?' in source ? "$source" : "'$(source)'"
-    join(["$(_src)"; [join(p, "=") for p in opts]], ", ")
-end
+# default options (for now)
+_read_opts = pairs((header = true, skip = 1))
 
-function reader(source::String)
-    _, ext = splitext(source)
-    if ext in (".csv", ".parquet", ".json")
-        return "read_$(ext[2:end])_auto"
-    elseif '?' in source
-        # FIXME: how to support other file formats?
-        return "read_csv_auto"
-    else
-        error("$(ext[2:end]): unsupported input file '$(source)'")
-    end
+function check_file(source::String)
+    # FIXME: handle globs
+    isfile(source)
 end
 
-function fmt_select(source::String; opts...)
-    sprintf("SELECT * FROM %s(%s)", reader(source), fmt_opts(source; opts...))
+function check_tbl(con::DB, source::String)
+    tbls = DBInterface.execute(con, "SHOW TABLES").tbl[:name]
+    source in tbls
 end
 
-function fmt_join(
-    from_subquery::String,
-    join_subquery::String;
-    on::Vector{String},
-    cols::Vector{String},
-    fill::Union{Bool,Vector::Any},
-)
-    exclude = join(cols, ", ")
-    if fill       # back fill
-        # e.g.: IFNULL(t2.investable, t1.investable) AS investable
-        include = join(map(c -> "IFNULL(t2.$c, t1.$c) AS $c", cols), ", ")
-    else if !fill # explicit missing
-        include = join(map(c -> "t2.$c", cols), ", ")
-    else          # fill with default
-        if length(fill) != length(cols)
-            msg = "number of default values does not match columns\n"
-            msg = msg * "columns: $cols\n"
-            msg = msg * "defaults: $fill"
-            error(msg)
-        end
-        include = join(map((c, f) -> "IFNULL(t2.$c, $f) AS $c", zip(cols, fill)), ", ")
+function fmt_source(con::DB, source::String)
+    if check_tbl(source)
+        return base_source
+    elseif check_file(base_source)
+        return fmt_read(base_source, _read_opts...)
+    else
+        throw(NeitherTableNorFileError(con, base_source))
     end
-    select_ = "SELECT t1.* EXCLUDE ($exclude), $include"
-
-    join_on = join(map(c -> "t1.$c = t2.$c", on), " AND ")
-    from_ = "FROM $from_subquery t1 LEFT JOIN $join_subquery t2 ON ($join_on)"
-
-    "$(select_)\n$(from_)"
-end
-
-# TODO: check_file -> check_source: file, file glob, table name
-function check_file(source::String)
-    # FIXME: handle globs
-    isfile(source) || throw(ArgumentError("$(source): is not a regular file"))
-    source
 end
 
 ## User facing functions below
@@ -82,49 +45,42 @@ end
 Store() = Store(":memory:")
 DEFAULT = Store()
 
-function read_file(con::DB, source::String)
-    check_file(source)
-    query = fmt_select(source; header = true, skip = 1) # FIXME: don't hardcode options
-    res = DBInterface.execute(con, query)
-    return DF.DataFrame(res)
-end
-
-function read_file_replace_cols(
-    con::DB,
-    source1::String,
-    source2::String;
-    on::Vector{String},
-    cols::Vector{String},
-    fill::Union{Bool,Vector::Any} = true,
-)
-    check_file(source1)
-    check_file(source2)
-    sources = [ # FIXME: don't hardcode options
-        sprintf("%s(%s)", reader(src), fmt_opts(src; header = true, skip = 1)) for
-        src in (source1, source2)
-    ]
-    query = fmt_join(sources...; on = on, cols = cols, fill = fill)
-    res = DBInterface.execute(con, query)
-    return DF.DataFrame(res)
-end
-
 function tmp_tbl_name(source::String)
     name, _ = replace(splitext(basename(source)), r"[ ()\[\]{}\\+,.]+" => "_")
     "t_$(name)"
 end
 
-function create_tbl(con::DB, source::String; name::String = "", tmp::Bool = false)
-    check_file(source)
-    query = fmt_select(source; header = true, skip = 1) # FIXME: don't hardcode options
-    if length(name) == 0
+# TODO: support "CREATE OR REPLACE" & "IF NOT EXISTS" for all create_* functions
+
+function _create_tbl_impl(con::DB, query::String; name::String, tmp::Bool, show::Bool)
+    if (length(name) == 0) && !show
         tmp = true
         name = tmp_tbl_name(source)
     end
-    DBInterface.execute(con, "CREATE $(tmp ? "TEMP" : "") TABLE $name AS $query")
-    return name
+
+    if length(name) > 0
+        DBInterface.execute(con, "CREATE $(tmp ? "TEMP" : "") TABLE $name AS $query")
+        return show ? DF.DataFrame(DBInterface.execute(con, "SELECT * FROM $name")) : name
+    else # only show
+        res = DBInterface.execute(con, query)
+        return DF.DataFrame(res)
+    end
 end
 
-function create_tbl_variant(
+function create_tbl(
+    con::DB,
+    source::String;
+    name::String = "",
+    tmp::Bool = false,
+    show::Bool = false,
+)
+    check_file(source) ? true : throw(FileNotFoundError(source))
+    query = fmt_select(source; _read_opts...)
+
+    return _create_tbl_impl(con, query; name = name, tmp = tmp, show = show)
+end
+
+function create_tbl(
     con::DB,
     base_source::String,
     alt_source::String;
@@ -133,21 +89,12 @@ function create_tbl_variant(
     cols::Vector{String},
     fill::Union{Bool,Vector::Any} = true,
     tmp::Bool = false,
+    show::Bool = false,
 )
-    check_file(alt_source)
-    if length(variant) == 0
-        tmp = true
-        variant = tmp_tbl_name(alt_source)
-    end
-    # TODO: support "CREATE OR REPLACE" & "IF NOT EXISTS"
-    create_ = "CREATE $(tmp ? "TEMP" : "") TABLE $variant AS"
-
-    # FIXME: don't hardcode options
-    subquery = sprintf("%s(%s)", reader(alt_source), fmt_opts(alt_source; header = true, skip = 1))
-    query = fmt_join(base_source, subquery; on = on, cols = cols, fill = fill)
+    sources = [fmt_source(con, src) for src in (base_source, alt_source)]
+    query = fmt_join(sources...; on = on, cols = cols, fill = fill)
 
-    DBInterface.execute(con, "$(create_)\n$(query)")
-    variant
+    return _create_tbl_impl(con, query; name = variant, tmp = tmp, show = show)
 end
 
 end